Back to an automatic today, and like the UNI featured a few days ago, this one is an early oscillating weight movement. The UNI Auto Dater uses the 2400 calibre, whilst the SM uses the 2410, so it is a slightly developed version of the same movement. Two variants were made with either 17 or 21 jewels, and as far as I can decipher, the ‘SM’ name is derived from ‘slim’ – these movement are certainly slimmer than the preceding Jet designs, so that makes sense. The date change is unusual, and maybe unique, on this movement and probably why it is designated 2410 – when the crown is pulled out to set the time the date can also be changed by rotating it backwards – anti-clockwise – something I’ve not seen in any other watch:

More info on the SM models here: https://sweep-hand.org/2011/07/24/this-weeks-featured-watch-11-the-sm/