If you like that 66 then maybe you should get the Model 77 goose call that goes with it and have the set,
I have both and they both are the best there was in their time. The 77 goose call breaks when you want it to and is one of the easiest to work goose calls I have ever used except for Gary's CCC goose calls.
The Olt model 66 is a very ducky call. I'm confident I could command ducks to land with one but I'm not taking my dad's old calls into the woods.
Good find and enjoy the 66.