Ultra rare, only one I've ever seen! Post war M1918a2 receiver wrench. tag reads:
M1918a2 cal.30 B.A.R
Wrench, Receiver (41-W-1998-625)
(6316005) New. . .
Stamped on the head is the # 6316005
USGI and appears un-issued. I always though this more of a collectable rarity than a usable item, although it's totally functional (I always used a padded bench vice for the receiver and a custom built barrel wrench for my builds)