A timely topic, as I'm looking for a way to mark the backs of my prints with some distinctive mark like a logo, as well as file, year, and serial no. information, and a place for initials or signature.
tshort, thanks for the link to the stamp company. Geoff, I'm with you about the intrusiveness of built-in signatures. I experimented with this also, but it just screamed to me "digital manipulation!!" and lessened the impact of the B&W images I usually make. I do the (hard-lead, very faint) pencil signature at lower right like you do, with only the year and serial number at lower left.
Along the same lines, has anyone heard of a "chop"? This as I understand it is a printmaker's device that is used to unobtrusively but distinctively mark the edge of a fine print (eg lithograph, etc) with the printmaker's distinctive mark, like a Chinese character or whatever. This is a nice idea for photographs if one can get the device made; perhaps the linked stamp-pad maker can do this.
Another idea would be to emboss the "chop" on the edge of the print outside the image area revealed by the mat. I've not found any embosser online other than those relatively large round ones used for "Ex Libris" and notary stamps, however.
Any other ideas?