I picked up a nickel wire lug Waltham O size wristwatch and when I opened it up it had a Riverside 21 jewel movement. I can;t find it listed in the Shugert Guide. Serial number is Ca 1927. Are these uncommon? Thanks
I have seen a fair number of these, mostly later Waltham movements. All that I have seen are actually 3/0 -- they share all of the same parts as the 0-size, but the dial plate does not have a lip on it, making it smaller.