577 & 577a are listed in the Scott U.S. Specialized Catalogue. The colors are listed as carmine (577) and carmine lake (577a). The small letter a indicates that this is considered a minor color/shade variety ... minor varieties are usually not listed in the Scott worldwide catalogue. I doubt that either of your stamps are 577a. My Scott lists 577a only as used with no value given. This frequently is the case for rarer items as there may be insufficient data to establish a price.
Under 577, my Scott also lists two shades ... carmine and light carmine. I would wager that these would likely be the shades for your two items.
Added: I checked the PF database and could find no certificates for 577a. But there are some 634b (carmine lake) ... the color for 634 is carmine. I found the difference to be subtle and a good many of the 634b submissions were deemed to actually be 634. You can see these for yourself ... go to the following link and do a search for 634b ...
www.philatelicfoundation.org/about/
Posted 12/11/2022 04:35 am
