Here is a U1 for comparison. The easiest places to look are at either side of the labels at top and bottom with "three" and "cents". U1 and U2 have virtually no space beyond the text; U9 and U10 have a bit more.
If you are dealing with entire, U1 and U2 frequently (but not always)have a red Nesbitt circular logo on the backflap. Those don't occur on U9 and U10 so that is a good diagnostic when present.
