Johnson Manufacturing RADIATOR TEST PLUG 3 INCH PN: 351-11 NSN: 4910-01-153-1823

RADIATOR TEST PLUG 3 INCH 

PN #S 3002-3INCH OR 351-11

NSN: 4910-01-153-1823

Diameter is 3 inch

Thickness of the plug is 1 7/8 inch

Total length is 3 7/8

The wing nut and bolt appear to be brass.