Color-Missing Errors

According to Scott specialized there are 4 types of these (not to be confused with Color-Omitted Errors)

Foldovers
Extraneous Paper
Misregistration
Perforation Shift

My question is regarding the 4th, a perforation shift.
I have come across a modern stamp (US 1970s) which I believe qualifies for a perforation shift color missing. This particular stamp is a single, and doesn't currently have a certificate. I would want to get a certificate for it.

Is it required to have at least 2 stamps demonstrating the shift of the color onto the second stamp and missing from the first stamp?

As a single there is definitively the missing color, but I suppose from an expertizing perspective you may not know if it could hypothetically be a and a color omit misperf. There isn't such a thing discovered with this stamp, but technically I wonder if it could be ruled out whether a single can get a perf shift missing certified.

As often noted on this board, please show an image of the item in question. Is you stamp large enough to be a complete stamp? Is there a design from the adjacent stamp showing inside the perforations? Etc.

Please post a picture without that no one can really tell you much.

I'd want to know if this would qualify 1557d

If you check the Scott listing for 1557 "a" and "d" both lack red; BUT the 1557d reads, "Red missing (PS)" with the PS meaning Perforation Shift. The 1557a is just red ink not applied as in "red omitted."

So you have a winner, the more expensive, but less complete, version of the stamp without red.

Get a cert if you wish, but that goodie is self evident.

Only the bottom row of stamps with selvage below are the 1557d stamps. The other 45 will be 40 change of design (text at bottom) and 5 misperfed incomplete design with all colors but most of denomination cut off.

excellent! Appreciate your help. I wanted to make sure I didn't need a 2 stamp minimum to prove it had red present on the above stamp, and thus had red missing on the below. 1557a are way more common, with datz putting est qty for those at 300-400 (6-8 sheets). My belief is the PS variety has a way lower number, for the reason you stated above. 1557's in general produced a lot of EFO's particularly around the red star placement, but only the particular scenario would produce this.

If I do ever come across a "transition" bottom-row with red on the stamp above, I'll upgrade. For now I'll take what I can get.

Less common, but less in demand