I recently bought an all matching 42 "byf" Mauser Luger known to some as the "Black Widow" model. I want to shoot it, but I fear breaking one of the all matching parts in the toggle assembly. I found a complete original 42 DWM toggle assembly online and was wondering if it has a chance to just drop in and function. I've read some snippets here and there that people swap the assemblies to prevent original parts breakage, but I want to make sure before I order it.

I think you have your dates mixed up in regards to the DWM toggle, as DWM stopped producing the Luger sometime in the mid to late 20's.  Having said that just be aware that Luger pistols were all hand fitted.  It's possible the DWM toggle assembly will work on your Mauser.  The best thing to is to lube it generously and manually operate the toggle to see how it's functioning.  You won't know for sure until you actually fire it.  There are quite a few mismatched toggle assemblies on Luger pistols and they are being shot without issue

Thanks for the reply. The toggle I'm referring to has a S/42 marking which I know to be a Mauser. Maybe the place I'm buying it from got them mixed up since they have a few for sale that I can choose from and they're supposed to be DWM. Either way it'll be here by the end of the week and hopefully it'll just work.

Well if we want to be picky, Mauser who made Lugers from 1935 thru 1942 bought DWM. Anyway to the question. You need to check headspace on the new toggle and "may" need to adjust the sear bar. Chances are it will work fine.