Help Needed -> George Washington Proprietary R13 & R18 Stamps

My dad and I bought a photo album that contained these stamps on the back of two pictures. We are inexperienced with stamp collecting as this a new hobby for me and my dad. I figured-out they are R13 and R18 stamps, but don't know what specific types these are (a-d) and what the value range might be as it appears that the range can be pretty big depending on the type/cancel.

Thanks!
Marc and Lou





*** Moved by Staff to a more appropriate forum. ***

The listings are based on whether the stamps are (a)imperforate, (b)part perforate (perforated on two opposite sides and imperforate on the other two opposite sides), (c) fully perforated as these are, or (d) fully perforated but on silk paper (which these cannot be; silk paper was not used before 1870, and the tax on photographs was from Sept 1, 1864 to August 1, 1866). These are R13c and R18c.

Minor correction: Photos were taxed from August 1, 1864 through July 31, 1866.

Mahler's book lists it as September, so perhaps I misread the tax on matches listed right above it. It is not really clear in the list at the back.

My go-to reference for Civil War photo-related tax information has always been Bruce Baryla's Civil War Sun Tax exhibit. My assumption is that given the awards it won, if information in the exhibit were inaccurate, someone would have caught it in the judging process.

Thanks, everyone! this was very helpful.