From Google. Definition of compound perforation : a stamp perforation having two perforation numbers, one for the top and bottom of the stamp and one for the sides
10.5 x 11 would be an example of a compound perf
I thought it might be that. Thanks for the clarification folks.
There are two other possibilities that are listed in the Stanley Gibbons Catalogue, but may not be in Scott. Both are kind of interesting. New Zealand SG 568, Scott 197 can be found with the top and bottom perf 13-14 which means that one side is Perf 13 and the other side is Perf 14. Cook Islands SG 100b, Scott85 has two columns of perfs from being reperforated.
