Scott NR 372 1/2?

Yes, the photo is a bit hard to see but it looks like a row of coil stamps.

First, A715 and A715a are not Scott catalogue numbers. They represent "labels" that designate a particular stamp design. There can be (and frequently are) multiple Scott numbers assigned for a specific design. That is what has happened with your George Washington example. The two different "labels" represent two different pictures of GW ... the first appears unshaven while the second appears cleanly shaven. Both designs were produced in both sheet & coil format. So you are correct, your picture is of a coil strip from a roll of stamps. Coil stamps will have straight edges on either the horizontal or the vertical sides.
Note that this design did NOT appear in any booklets. But if it had, you might very well have found stamps with 2 adjacent straight edges or a single straight edge. For an example of where this might occur, look at design A650 (another George Washington).