S&G padlocks are evil. They are hateful devices. The inner working are broadly similar to the full-sized dials but are fiddly little demons. Changing their codes never goes properly, and recovering from a lost code requires multiple special keys. I know of boxes containing dozens of "bricked" S&G padlocks that people have given up trying to use. The difference in design and build quality makes it hard to believe both are made by the same people.
Same company makes both combination dials and the large padlocks like the 831, 833, 851. I was lucky enough to tour their manufacturing facility, it's a typical machine shop plus a small foundry as they do their own casting on-site too.
https://mbausa.com/content/downloadfiles/8077_Combo_Recovery...
https://mbausa.com/s-g-padlock-combo-recovery-set/
Compare with the easy change procedure for dials: https://homelandsafes.com/how-to-change-the-combination-on-a...