Setting ISO on Yashica T3?

Is it possible to set the ISO on the yashica T3? The only thing I can think of is to print out 1600 DX codes and tape them onto my triX rolls.

DX codes are read electrically. Standard ink printing would not work. For substituting cassette DX coding, either stick-on Aluminium foil and then cover it again with plastic foil for isolation resembling the respective coding or use ready-made coding stickers.

I bulk load film and use old cassettes (with the leader poking out, to tape onto) -- you could find some 1600 speed cassettes to use that way, as a hack.

Thanks for the information. It led me to find these http://www.firstcall-photographic.co.uk/products/746/firstcall-dx-recoder-labels-iso-200

One could also scratch-on the needed pattern, but then would have a corrosion problem at that surface on long time.

You can simply re-spool your film to a cassette with the desired ISO. You can do this with by cutting the leader of the film, stitching the film to the remaining part that comes out from the used target cassette with some scotch tape, respooling the film from one cassette to the other and making a new film leader at the end. Beware that with this trick the numbers will come in the opposite order from the 36 (35 or 34 actually) to 1 but this is not really a problem and you have to remember that the last 1-2 frames will be fogged and with scotch tape on them (stop shooting just before the end and load a new film).
If you have some old DX coded type re-usable cassettes you can simply move the film from it's cassette to an other with the desired ISO.
Of course in both tricks, you have to do some actions in total darkness.
I do these tricks with my Olympus MJU-II and some expired films (that I want to shot at half or less ISO speed), it works all the time.

I scratch off paint or apply packing tape as needed to the ISO coding squares to change the cassettes. There are many diagrams online to show how the coding works.