I purchased a set from Freestyle while Thomas was still in business. I bought a yellow tape, a red tape, and a black tape. I took them apart a few years later to see if they were filters I could replace myself for less money. In the yellow tape filter I found two sheets of gel filter material. One had the number 3407, the other 3406. I recognized them as Rosco filters from my sample book. The red tape had "ROSCO 19" printed on the edge of the filter. The black tape did not have any markings, but were the same colors as the yellow tape, but used more layers of filter material inside. All of them used the tissue paper that comes with Rosco filters as the diffusion material.

The numbers were not present in both filters of a pair. I don't think they were intended to be left on the filter material when cut and put in place. I had a very old set of Thomas Duplex filters, and they were different material. It was far too old and faded to tell what they once were. It is possible that the filters sold for these safelights now and just before Thomas Duplex stopped selling their lights are made by someone else and they just use what they think may work, but if you buy a set of filters from Freestyle or KHB Photographix, these are what you get.

You could always buy a set, open them, and tell us what is in them. If they are different than what I have, then I was sold the wrong filters. But I doubt it.