This is a Dynacorn fuel gas sending unit made from 3/8 inch stainless steel, designed to fit the 1964, 1965, 1966, 1967, and 1968 Mustang, as well as the 1967 and 1968 Cougar.
It's a brand new, vintage-style replacement part.
The manufacturer part number is T03A.
Stainless steel means it won't rust like the original mild steel ones did, so this is a long-term fix.
If your fuel gauge is reading wrong or not at all, this is likely the culprit.