Recently I have some thoughts on the nature of many popular Sea-gull movements that is commonly seen. In another post these thoughts sort of flew out of my mind but the previous thread was already crowded enough as it is. So here I am reposting them and start a new discussion.
This is what I wrote
What I had in mind in terms of original was more towards workhorse everyday movements. I think from a horological point of view, the progression of improvements on an original design is what I find highly respectable. We see it alot in the popular VCMs, such as Shanghai 581 evolved to 611 ~ 1120 etc. Or Beijing's BS-2 that evolved into BS-5. Later, we even see Tonji evolved and became the even more refined Shanghai B. In all those examples, Chinese manufacturer started with one design and modified, simplified or improved on those well tested models. By copying other popular Swiss and Japanese designs in their modern offerings, Sea-gull has gain exposure and popularity in the West. But it may be impossible to shake off that impostor image in the foreseeable future. It saddens me to see such fate on this historical and truly beloved VCM brand.
MHe225 kindly shared this link and its contents (correction -originally posted on Chinese Watch Industry Wiki )
The Origin of Clone Movements
Although some current Chinese watch movements originate from foreign designs, these likely have not been developed specifically to build fakes. Development and manufacture of mechanical watch movements are only within the means of major, established enterprises with too much to lose if caught building counterfeit watches. However, clones of popular Swiss and Japanese movements seem to have been developed primarily to accommodate demand from 3rd party OEM makers. Some of these manufacturers sell quantities of 'cleanskin' watches, which of course may easily be converted into fakes. Similar market forces drive the development of 'look-alike modules' i.e. generic movements with enhancements to produce a dial layout similar to a famous Swiss watch.
It is a myth that 'Asian ETA/Valjoux/Unitas' movements are made by Chinese companies using ETA tooling. A careful examination of ETA movements alongside their Chinese equivalents reveals some subtle differences. The Chinese designs appear to be adapted to simplify manufacturing and assembly and to enhance durability. There are other differences that are simply...different. Sea-Gull, Hangzhou, Liaoning, and Shanghai watch factories have all had to create their own tooling to produce these movements.
Common Swiss Movements and their Clones
ETA 2824-2 - ETA's basic automatic winding, twenty-five (25) jewel movement which traces its roots back to the 1950's.
» Near-exact copies of the 2824-2 are produced by Sellita (the SW200) in Switzerland and by Hangzhou (the 6300), Sea-Gull (the ST21) and Shanghai Watch Factory (designation unknown) in China. The Valanvron watch company in Switzerland assemble and finish ST21 ebauches as legally 'Swiss Made' movements, designated Valanvron 24.
Detailed comparison: How do Seagull and Hangzhou compare to a ETA: An in-depth look...
ETA 2836-2 - The day/date variant of the 2824-2
» Near-exact copies of the 2836-2 are the Swiss Sellita SW220, Chinese Hangzhou 6311 and a Sea-Gull ST21 variant. The Valanvron 36 is based on a Sea-Gull ebauche.
ETA 2892.A2 - ETA's more upscale 2892 is an automatic winding, twenty-one (21) jewel movement fitted with top quality components, with its design dating to the 1970's. Owing to it's relatively slim height of 3.60mm, the 2892.A2 provides a good platform on which to add or build a chronograph complication.
» The Sea-Gull ST18 is a near copy of the 2892. Valanvron assemble and finish ST18 ebauches as Swiss Made movements, designated Valanvron 92.
Detailed comparison: An ST18 and an ETA 2892-2, a review
Valjoux 7750 - The ETA/Valjoux 7750 is a widely used automatic winding, twenty-five (25) jewel chronograph movement, which can be fitted with a variety of features including the triple date (day, date, month and moon phase) or a variety of two and three register models with totalizers or counters for minutes, seconds and hours.
» Various Chinese clones of the 7750 are manufactured by the Liaoning Watch Factory and the Shanghai Watch Factory. Non-Chinese clones include the Swiss Sellita SW500 and Russian Maktime 30664.
Unitas 6497-1 - The ETA/Unitas 6497 is a large, manual winding, seventeen (17) jewel movement, often fitted with a subsidiary (small) seconds complication in the 9 o'clock position. Originally intended for pocket watches, the 6497 has seen a recent resurgence in popularity due to its association with Officine Panerai wristwatches and homages.
» Hangzhou's 9000 series is a near copy of an earlier version of the 6497/6498, whereas the Sea-Gull ST36 is closer to the current ETA version. Both Hangzhou and Sea-Gull versions are available in skeleton versions that stylistically differ from the ETA version.
Venus 175 - A hand-winding movement with column-wheel controlled chronograph with 30 minute totalizer, no hour totalizer. Production ceased in the early 1960s.
» Strictly speaking, the Sea-Gull ST19 is not a 'clone' of the Venus 175, as it is descended directly from a movement built on the same tool-set as the original Venus, transfered to the Tianjin Watch Factory in the 1960s for production of a watch exclusively for the Chinese air force. This ancient design was resurrected in the 21st century, and subtly but extensively upgraded to become the ST19. Due to its use in fake Omega Speedmasters, it is occasionally (and very incorrectly) referred to as a 'Lemania clone'.
From time to time, luxury Swiss watches are offered featuring refurbished vintage Swiss movements, including the Venus 175, however examples have emerged where Swiss companies have used the ST19 and claimed to use a vintage 175. Any such watch featuring more than 19 jewels and an escapement 'upgraded' to 21,600bph should be assumed to be a mis-labelled Sea-Gull ST19.
Note: A thorough comparison of Sea-Gull's clone movements and their ETA counterparts can be found on the TZ-UK forum (edit: link is broken)
Common Japanese Movements and their Clones
Miyota 8205/8215 - The Japanese made Citizen/Miyota 8205/8215 and 82S and 8N series variants are among the most popular off-the-shelf automatic movements used worldwide by OEM and proprietory watch manufacturers due to their robust nature and low cost. These movements are able to hand wind, but auto-wind in only one direction and lack a hacking (seconds stopping) function. The escapement beats at 21,600bph (6 beats per second).
» Chinese-made clones include the Dixmont Guangzhou DG28/38 series and near identical Nanning NN28/38 series. In their basic form these movements exactly match the dimensions of the Miyota movement, enabling them to compete directly for some of Miyota's established clients. Their most significant difference from the Miyota is the wide range of functional enhancements available on these movements, which gives the Chinese manufacturers a competitive edge in the marketplace. For example - the ability to offer a watch assembler both a day/date and a GMT complication compatable with the same case dimensions. Unlike the Miyota, the DG and NN movements have a hacking function. Fujitime is an example of a watch company that has switched from Miyota 8205/8215 to DG28. The DG/NN design may be visually distinguished from the Miyota by a stepped top plate with prominently chamfered holes for the jewels on the edge of the step.
Fujita offer a basic version of the DG/NN design, possibly finished from a bought-in ebauche. Qingdao Zixin have also produced some variants of the Miyota clone. The Beijing Watch Factory make a version of this same design, distingishable by a different shockproofing device, and usually a very high quality of finish. Elaborately decorated skeleton versions are produced, along with many unique calendar and dual-time functions.
» The Sea-Gull ST16 is also greatly influenced by the Miyota design, but with significant differences in the auto-winding mechanism, which is based on the Seiko system. Like the DG and NN movements, the basic ST16 is also dimensionally compatible with the Miyota, but also hacks. The revised ST17 positions the 4th wheel at 6 o'clock to better suit a seconds sub-dial, while retaining the Miyota dimensions. Both the ST16 and ST17 have a separate plate for the auto-winding module, making them easy to distinguish from a Miyota movement.
The excellent reputation of Miyota automatic movements has led to some on-line sellers claiming a 'Miyota' movement in watches using the DG or NN movements. The Croton watch company even goes so far as to designate the the DG28 used in their watches as 'Japanese CR8215 movement' and their sellers claim it is a 'modified Miyota'. The rotor is marked 'Japan', even though the DG logo is clearly visible below the balance wheel. Similarly, their day/date 'Japanese CR8205 movement' is in fact the Sea-Gull ST16.
Seiko 7009 - The classic 7009 movement is one of the most produced movement calibers in the world. Developed from earlier Seiko movements featuring the patented 'Magic Lever' winding system, the 7009 has the winding mechanism mounted directly on the top plate of the base movement, with the pawl on an off-set wheel engaging the rotor.
» Hangzhou's 2000 series of movements are based on the Seiko 7009. Hangzhou offers many complications for this movement series, most of which were never available from Seiko. The use of these movements in some counterfeit Seiko watches has led some to claim these movements were designed specifically for that purpose. However, given the costs associated with designing and tooling up for production of an all new movement, and the many un-Seiko-like enhancements also offered, it is far more likely that the movement was created for more general use, but its similar appearance to the Seiko 7s26 makes it attractive to fakers.
Orient 469 - Developed in parallel with the Seiko 7009, the base movement is almost identical, however the auto-winding uses the original Seiko arrangement of a rotor mounted on a bridge, with the 'Magic Lever' pawl attached directly to the rotor hub.
» A clone of unknown origin enjoys extensive use at the budget end of the market, especially short-lived brands from Shenzhen. An early client for this movement was Orion, Moscow. The Orient-clone is available in solid or skeleton, with date, day/date and day/date/24-hour options. The plates are often decorated with an etched and polished stripe pattern. Quality is generally lower than the Hangzhou 2000. Some sources state a Shanghai origin for these movements, and Golden Time seem likely, but firm evidence is lacking. Some on-line parts catalogues list these movements with the prefix 'SP'
» Fujita offer a basic day/date movement of similar design to the Orient clone described above, but with a differently-shaped auto bridge and a flange on one finger of the pawl. Standard of finish is poor. No other manufacturer is known to produce this design so it is probably an in-house design. Like the Hangzhou 2000, some of these Fujita movements have appeared in fake Seikos.