Swiss #31 Validation Question

Hi folks,
I am having some difficulty identifying this stamp. It was labeled #31 in the old stockbook I am working on. I measure the thickness at 0.09 mm on my digital calipers. Any help would be greatly appreciated.

Thanks in advance,
Chris

It is Scott 31. There's no other 1fr with a yellow thread. Whether it's thin paper, I can't tell from the scan.

Be aware if you are using mechanical calipers/micrometers, you're doing it wrong. Those will compress soft things like paper, distorting the measurement. You either need to use a mechanical paper thickness gauge that only momentarily contacts the paper or one with a digital reader/scanner. This stamp is embossed so unless the white paper outside the design is measured, your measurement might be deceptive. Compare paper with others of the series/issue (or the earlier one) if you can.

Thank you, Hy-Brasil. I was careful not to compress the engraving so I am sure that my thickness measurement is on the high side. I'll see if I can find a nearby dealer to check thickness for me. It feels very thin but thin is only relative to what the thicker 31 measures. The stamp is in pretty rough shape with a missing corner, two tears, a crease, and having been hinged.

Thanks again,
Chris