These gauges have been laser cut from stainless steel according to the dimension drawings on page 20 of the 1944 MG42 armorer's manual HDv 181/7.
The pressure plate gauge checks the curve of the finger which guides the cartridge from the belt and into the chamber. Hold it up against the pressure plate (knob goes forward). If it doesn't match, correct the pressure plate till it does.
The firing pin gauge has a Min. and Max. recess for checking the firing pin protrusion. Remove the bolt housing from the bolt head. Slide the bolt rollers to the outside, push the firing pin holder fully forward. Use the gauge to check how far the firing pin point sticks out.
The little hook should slide under the extractor. If it doesn't, then a cartridge probably won't either and there's a problem. The slot with the rounded bottom is for checking the contour of the firing pin point. I guess it's for when you need glasses and don't have them, so you can see if the point is deformed.
Pictures are below. 1/16" thick stainless steel, laser engraved as shown.
$30 for the set, delivered by first class mail to US addresses.
Tools are sold as a set. If you only want one, it's OK - but let me know which one you want for $30.
Foreign sales are fine, postage is at actual cost. Check or money order is good (address is below).
Paypal is OK, but add $1 to help cover cost ($31 total).
5678 State Rt. 45
Lisbon, OH 44432
Get 'em while you can. This was way too much trouble to do another batch, so when they're gone, that's all.