I am not a "Smith" and my knowledge very limited on this subject, I have researched it on the internet, and talked with my smith. He has a very unofficial way of testing, he takes a scribe and if he can put a mark on the locking lug by hand its a little soft. Some of the Mausers manufactured in the 40's benefitted from the correct heat treatment. Some manufactured around the turn of the century (1900), got the correct heat treatment, some did not.
I just do not want to take a chance after I have spent all that money and work, for something to go south, and then there is all my work, money, and possibly and injury to boot, I figure it is cheap insurance. Mr. Sterling said they have done a couple of thousand, there seem to be some others that feel that way to, blame it on my anal retentiveness I guess