This is probably one of the most difficult of the Washington-Franklin head series of stamps to identify. Some collectors do not understand where to look for the difference.
There are several different types of design used for the 2¢ red Washington stamp. The difference between the very common Type I stamps and this scarcer Type Ia stamp is very subtle.
First of all, Scott #500 is a flat plate printed issue on unwatermarked paper and perforated 11. If your copy does not have those characteristics, it cannot be Scott #500.
Assuming your copy exhibits those characteristics, how do you distinguish between the very common #499 and the more scarce #500?
Draw two imaginary horizontal lines on the stamp. One line would go through Washington’s lips and the other horizontal line would go through his nostrils on the bottom of his nose. That creates a space of a few millimeters wide on this stamp. Following from left to right, you’ll run into an inverted “Y” shaped white space that slightly curves to the right. This represents Washington’s sideburn.
Washington’s cheek is made up of a series of horizontal lines that end where the sideburn begins. You want to look at the bottom 5 horizontal lines which fall just above the imaginary line from his lips and just below the imaginary line from his nostrils. Look at the leftmost side of the sideburn.
On the common Type I stamps (#499), the horizontal lines of the cheek are not joined by a vertical line. On very heavy prints of Scott #499, the bottom one or two lines of the sideburn may appear to be joined, but never all four horizontal lines.
On the Type Ia stamps (#500), the bottom four horizontal lines of the sideburn are joined by a light vertical line. The key here is that all four horizontal lines must be lightly joined together. If five horizontal lines are joined together, that is a Type II stamp. If none of the lines are joined together or only the bottom one or two horizontal lines are joined together, that is a Type I stamp. Again, the key is that the four horizontal lines must be joined together by a light vertical line of ink.
My recommendation is to use at least a 10x magnifier to see the difference. I prefer a 30x magnifier for this kind of detail. I also sometimes use a Zoom digital microscope that connects via a USB port to my computer.
As of this writing, a used or mint, hinged copy of Scott #500 is priced at about $250 in the Scott US Specialized catalog. It’s not cheap, but probably within the means of many collectors. You could pick up a very off center copy for a fraction of that price, especially if the off center copy also has small faults like a thin or clipped perforations. A space filler copy of Scott #500 is more affordable and can serve as a reference guide in identifying other #500 copies that you may have.
Before you ask, no, I am not going to go through an accumulation of perf 11 copies that you have to look for Scott #500 for you. I have, on occasion, looked at a single stamp that someone thought was a #500. Identifying #500 takes some non-trivial effort and it just is not possible for me to go through an accumulation of #499 copies looking for a #500, no matter how small the accumulation. That exercise is left to you, the reader.
There is a website that can help too. Go to http://03a1e30.netsolhost.com/1847_landing.html which is an archive of the 1847.usa website. There is a link for the “2C Types 1-III” on the left. Click on that link and it will show you all of the differences in this issue. There are detailed images of the Type I and Type Ia stamps that may help you too. It’s a good resource to use. I recommend using it.
For completeness, there is an imperforate variety of this issue too. Scott #482 is the imperforate Type I variety. It is very common and has a nominal catalog value of about $1 or $2. Scott #482A is the imperforate Type Ia variety. This stamp is very rare. All known copies of #482A are used and all of them have Schermack Type III private perforations. These were private perforations applied by the Schermack Company to provide stamps from private vending machines. The Type III perforations are two vertically oriented rectangular holes. If you want to see an illustration of the Schermack Type III perforations, they are illustrated in the Scott US Specialized catalog in the “Vending and affixing machine perforations” section of the catalog.
Again, I mention this for completeness. But #482A is so rare; most collectors are likely not going to have a copy.
Good luck identifying your perf 11 flat plate issues that are unwatermarked. I hope you are able to discover a copy of Scott #500. It is scarce, but finds like this are more likely to happen than finding another copy of Scott #85A.