Brass i.d plate

I have what I believe maybe an aircraft i.d plate of some sort. It measures 2.5inch by 1.5 inch. It has the followinf on it:

Serial No. 16502144
Date MMORSR
Drg No. QOV Issue No. 1
Test pressure 50 lbs/sq ins
Max out temp. 120c

the drawing number might be QCV as it is badly stamped, The test pressure was originaly 20 but has been over stamped. So the qusetions are is it avaition related? if so what is it? and from what?

Thanks for any suggestions.