[John Sabato]

I would use the 50/50 ATF and acetone to soak and use with a stiff plastic bristle brush to clean it as much as possible. Soak a day at a time, then use the brush in the solution, and repeat until the gun is as clean as it will get.

Once the dirt has been removed, you could try removing some quantity of rust using the electrolosis method, but check it frequently because the gun is mostly rust now.

Neither of these methods should pose any danger to you... even if there is a cartridge in the chamber.

I doubt you will successfully dismantle this gun without destroying what is left... so once it has all the dirt off of it, I would mount it on a plaque with an inscription of where it was found with your name and date.

Please do elaborate on how the gun was found after all this time... metal-detector?

Welcome to the Lugerforum and thanks for sharing your historical find.