Did Gibson stop making the Pancake body in 1973?
Yeah... 77 was the transition year...
There were some exceptions, like mostly late 76 Customs with non pancake body, it was transitional period.
Interesting question is, why they added another extra thin veneer under maple top. It wasnt perhaps to lower the production costs.
That looks like an early 70's custom with the thin binding in the cutaway. A 76 custom I'm looking at now has wide binding in the cutaway like a 70's Deluxe. The 73 has narrow binding in the cutaway like your pic. Here's a quick shot comparing the binding width in the cutaway... '73 on the left, '76 on the right: