Brand seems to be "Ladura"--can't find anything on this? Not sure how to take it apart, so looking for info that could be gleaned from external observation. The only other visible markings on it are the standard U.S. patent numbers [US PAT 2640668 US PAT 2719402]. Says it's 17 jewel, shockproof--seems to run beautifully (keeps accurate time). Wondering about the value, should I have it serviced and/or cleaned? (verdigris patina seems to indicate brass casing) Also assuming it comes from the 1950's? Any insights will be much appreciated! Thanks!