You can download and print a perforation gauge here
http://stampsmarter.com/learning/Fo...rfGauge.htmlSince the stamp is on the booklet, you can easily cut the paper perf gauge so that you can then line it up next to the stamp, find the one that best matches the stamp perforations. It should be either 11 or 10 1/2; the tops/bottom might be different then the sides of the stamp.
Note: do not soak the stamp off booklet.
Don