OLSONGO wrote:Tonio, the measurements correspond more to a quinto and a conga.
Just to add what BnB said, while the head measurements are indeed what we would think of today as quinto and conga, sizes were different/smaller back when these were made. And the shape of the drum - the whole profile - has a major impact on whether a drum is quinto, conga, tumba or whatever. (I know you know this, Oslongo, but I'm just pointing it out for anyone who may not). Check out this photo of 3 old Gon Bops quinto/conga/tumba.
As for old Gon Bops sizes, here are some photos I took from a 1972 catalog I have. The sizes listed here are for the International Series, but all the GB series had the same sizes. [obviously, Q=quinto, C=conga, T=tumba. L=large]. I'm pretty sure they measured the diameter across the top before the bearing edge was cut.