The stamp below was listed as a common R13c for $2 shipped.
Even though the centering is awful (although most were centered poorly) and has faults, it is worth more than $2. It's not an R13c, but the much more scarce R13e (ultramarine) which catalogs $300.00.
Even though one cannot rely on a seller's pictures for color accuracy, in addition to the hue there were additional markers that fell in line with the possibility of it being an R13e:
1. Soft impression. When compared to an R13c, the R13e always looks softer and not as well defined.
2. Late (1870) cancel date. The ultramarine inks were a late adoption in the run of 1st issue revenues.
Even had it not panned out, it was a worthwhile gamble. Knowledge is power.

