I have a Flat Latch model 36 no dash and the trigger was serrated. BTW, it's a Sock Drawer Special, no evidence of any firing at all when I got it and pin prick rust spots on the side plate. Which makes it a shooter so it's now been well shot. After the first time using it I got out my dremel and took care of that bundle of razor blades. Now there are enough of the serrations left to provide traction but it won't leave you bleeding after shooting a box of 38 specials. Other issues was a mainspring that produced a 15 lbs. trigger pull in DA and the factory wood grips were much too tiny. Installed a Wolff spring kit, polished the spring strut, and replaced the factory grips with a Hogue monogrip. One of these days I'll get around to boiling the side plate but for now I keep it waxed.
BTW, some may be a bit disappointed that I "tinkered with an Original" but it was a flawed original and not worth spit as a defensive handgun. BTW, what idiot decided tiny grips that require resetting the hold on the gun after every shot thought that was a good idea. The older I get the more I get peeved by flat out stupid "engineering" choices. Really, a defensive handgun and they put grips on it that effectively made it a single shot firearm.