Flyingdutchman has written some excellent points. I personally would add one point which perhaps is the most difficult: See, if the engraving conforms the german language "style" and the german "style" of these times.
Somebody said "if you want to collect german items you have to understand german" and this is NOT meant in ANY political way and not limited simply to the german language. It goes into the direction of german feeling of these times.
As most faked inscriptions are made out of germany, mostly in not german speaking countries, mostly by not german speaking people, there are often a lot of minute errors which at least can lead to suspect. Yes, I know that also period inscriptions have not been flawless all the times, but I personally would avoid these also in each case.
Regards,

wotan, gd.c-b#105

"Never look for sqare eggs" as a late owner of an original FHH-dagger used to say.