That is a real deal early US gold coin in there. Appears to be in really good condition also. 1.7mm for an approx. The diamonds have SI2/I1 clarity with G/H color. 1 7/8" (48mm) north to south including the bail by and 1 5/8" (41mm) east to west.
The bail opening is 4mm. It is fully hallmarked, tested, and verified weighing in at 17.9 grams.
Comes from a clean, smoke-free home.