Odd Perf Variety For Old Glory Stamp

I have a stamp that matches all characteristics of 2883 except it is perforated 11.25 x 11.15 instead of 10 x 9.9 (as specified in my 2011 Scott Specialized). I have measured the perfs very carefully, and I have checked the stamp against a copy of 2881 to be sure the edges hadn't been cut. It is uncut and is the exact same size as 2881, but with the left and bottom edges unperforated.

I wonder if the perf 10x9.9, as stated in my catalog for 2883, is an error and possibly was corrected in later versions of Scott. I also wonder if there is a perf 11 variety of a booklet stamp of this design (black "G", "For U.S. addresses only") that I have overlooked.

Any help appreciated!

I see the 2881a (A2208) listed as perf. 11.2 x 11.1 in a booklet of 10. Could that be it?

KGB
I think you are right. Since 2281 is a sheet stamp, I wasn't considering the "subheading" "a" to be anything but a variation of the sheet stamp, so I didn't look carefully. Thanks for the heads-up.