I thought I’d write this because I happen to own both (at the moment), and because I prefer the Gen 1 though the Gen 2 is more popular.
Gen 2 differences:
- Thinner by 1.9mm (13.8 Gen 1 vs 11.9 Gen 2)
- Powered by a Sellita SW300 with 42 hr pr, Gen 1 uses an Eterna 3090A with 65 hr pr.
- Crown is smaller and has crown guards, the Gen 1 is larger with no crown guards
- The bezel is narrower by about 1/32”
- The date wheel is considerably more conspicuous and perhaps (?) more legible.
- The bracelet length can be adjusted on the fly with no tools.
- The crystal is flat whereas the Gen 1 is slightly domed.
So let’s take a closer look.
The Gen 1 is 13.8mm tall or thick vs 11.9 for the Gen 2, both cases are 40mm.
The reduction in 2mm was achieved by swapping out the 5.6mm thick Eterna Caliber 3090A for the 3.6mm Sellita SW300 and using a flat crystal. Thinner is nice, but I prefer the slight domed crystal as it adds a pleasant aesthetic, a little nuance to the look. Monta says the flat crystal improves legibility, and I find this is slightly true only because the dome reflects a much larger area than a flat crystal (think car’s side view mirrors that say “Objects are closer than they appear”), though in actual use I do not find this to be a problem.
The other reason a domed crystal would impair legibility is distortion when viewing the dial from the side. But with the slight amount of dome on the Gen 1 crystal, this is not an issue.
The Gen 1 uses the Eterna Caliber 3090A with 29 jewels, 30 x 5.6 mm, 28,800 vph and 65 hr pwr res. I like the 65 hours. 50% more than the ETA. It will easily make it through a weekend of non-use. Here is decent article on the Eterna movement: https://www.hodinkee.com/articles/di...rna-caliber-39
The Gen 2 uses the Sellita SW300 with 25 jewels, 25.6 x 3.6mm, 28,800 vph and a 42 hr pwr res. This movement is a clone of the ETA 2892 clone which is a finer movement than the their 2824.
ETA movements article: https://www.gentlemansgazette.com/eta-watch-movement/
The Gen 1 is a little wider and the zero marker triangle is more prominent. I prefer the slightly wider bezel for a bit more robust look, and the filled in triangle I prefer for legibility. In the picture above, notice that the the zero triangle on the Gen 2 is not even close to the legibility of the Gen 1.
The Gen II has it, the Gen I does not. This can be an important factor in actual diving, or timing in low or no light, or it may be irrelevant if you never use the bezel when its dark. I frequently use the timing bezel but can’t recall needing legibility in low or no light. They are both adequate for my purposes.
The Gen 1 uses a substantially larger crown which, coupled with the lack of crown guards makes for an exceptionally easy grip which I appreciate every time I set or wind the watch though it is unusual to produce a dive watch without crown guards. The Gen 2 crown is actually not so easy to grip when screwed down. The Gen 1 crown has, on occasion, caused some discomfort on the back of my hand though the past few days of wearing has been without issue. Some find the Gen 1 crown more appropriate for a pilot watch and not proper for a dive watch.
The Gen 1 is white on black and the date window supplants the 6:00 marker making for a much less conspicuous date display than the Gen 2 with its white background and position above the 6:00 marker. I find the Gen 1 date display to be nicely camouflaged on the dial.
While the bracelets are the same, the big difference are the clasps. When closed, they both look the same, but the Gen 2 clasp features a nice design that allows you to change the sizing on the go with no tools.
In the photo below, the locking center link, which you can’t see, is open allowing for adjustment. The side portions of the link are laying flat inside the clasp and can slide back and forth to adjust.
In the picture below you can see the center link with its spring loaded ceramic ball bearing that provides a detent to help keep the center closed when removing or putting on the watch.
In the picture below the center link is just shy of its closed position.
I like an on-the-fly adjustable clasp. Sometimes they are handy, like on a hot day or when working out at the gym. I much prefer them to be concealed, like the Monta, and I love the ones that allow downsizing while wearing, not a feature of the Monta. Also important, of course, is the adjustment must stay put, which unfortunately the Monta does not when off the wrist. When the watch is worn, the adjustment is secure, but when removing or putting on the watch, the lock link frequently opens and changes the adjustment. I am curious if others experience this. It is enough of a bother that I prefer the Gen 1 clasp.
In sum, from my perspective, the differences are small and its a matter of preference. My preference is the Gen 1. I like the slight domed crystal, slightly wider bezel, the almost-not-there date window and that 65 hr power reserve. If thinness is paramount, then the Gen 2 trumps.
Which do you like better?