Anyone know this fixer

Clearing out my dads darkroom we found ten tins of fixer. The attached shows a can. It makes 5 Gallons, states to mix at no higher then 80F. The labeling is:
6525-612-1885
Fixer/X-ray processing power
Worthy Chemicals
Anyone know if this is just Sodium Thiosulfate or if there are other components. It is a power and not the pentahydrate crystalline form, making identification not so easy.

Are there ways to identify? Can I judge from the pH of the mixed solution?

All comments welcome.

It is probably sodium thiosulfate since all rapid (ammonium thiosulfate) fixers I've seen are liquid concentrates. The warning against mixing at higher than 80 F also suggests that it is in fact sodium thiosulfate. Mixing that type of fixer at too warm a temperature yields a cloudy solution. There is nothing at all wrong with sodium thiosulfate fixers, and you can use them as you would a rapid fixer. Fixing time takes longer, that's all. Goodness knows how old this stuff is though. The address does not use a zip code, but is labeled "Brooklyn 21, NY". Zip codes went into effect on July 1, 1963, so this stuff is obviously older than that. I'm a native Brooklynite, and I can tell from the zone number that the manufacturer was located somewhere in the Bushwick section (one of the original Dutch towns that later became the city of Brooklyn), not far from the Williamsburg Bridge. Is the fixer still good? Beats me, but if the can is intact (not rusted through) and you feel like mixing up 5 gallons of fixer, give it a shot.

Is there a street address anywhere on the can? If there is, would you let us know? I'd like to go see what's there now.

Fixer is pretty easy to check if you are willing to mix up that much. If it is not totally caked and will go into solution try to clear a scrap of film. If it clears in a reasonable time you are good to go. I would assume as Frank said that it is sodium thiosulfate based. I bet my old copy of the PhotoLab Index might have a formula, but if you have a need for a GP fixer you may be good for quite awhile!

Oh yeah, another thing. If you mix it up and it smells of acetic acid, it's obviously an acid fixer. All acid fixers of that type will contain sodium sulphite as a preservative, or else the acid would break down the thiosulfate in short order. If it is acidic, it probably has a hardening agent incorporated too. Considering the kind of treatment x-ray films get, it is likely so.

The Number 6525-612-1885 is a NSN (Military stock number) which is in the "old" format so it is from the Korean war era rather than Vietnam era. The 6525 is the prefix for X-ray materials so that is consistent. The newer format would be 6225-XX-YYYY-ZZZZ and is sometimes refered to as a NATO number.

For the record; this is probably sodium thiosulfate, but I know at least two fixers that contains ammonium thiosulfate even in powder form: Tetenal Variofix and Calbe A300. The A300 is based on ammonium and sodium thiosulphate in a ratio of 2:7, according to official sources at Calbe. While I don't know for sure, I think these two products could be identical. This probably has no effect on normal printing, but with alternative processes and lith printing, they bleach more than plain sodium thiosulfate does.

Thanks to all for the input and additional insight on what may be inside. Just back from a thousand mile drive, I'll be testing a batch next weekend. Frank no other address on the can, so you can't find what is there now. With the zip code changing in 63 and the old style MIL numbers and the fact that my dad and I shopped at the surplus store from 67-71 would put the date of manufacture in the 50's to early 60's .

BTW in the 'stash' we found a pound each of potassium ferrocynide [sic] and of hydroquinone

TR

The can shows a federal stock number, so the fixer is probably military surplus. The can also shows a postal zone number for the company, rather than a zip code. The can is most likely from the late 40s or 50s. The can says (I think) XRAY PROCESSING POWDER." I don't see "fixer," but I'll take your word for that being somewhere. X-ray fixers are generally a quite a bit more concentrated than ordinary fixers, and you have to be careful not to overfix. Overfixing with them can very easily cause bleaching of the image. I agree that it is probably a sodium thiosulfate fixer. From the estimated date, it is probably an acid, hardening fixer. Fixer ingredients are stable, even when mixed together, when kept cool and dry. If the cans are in good condition, there is a good chance that the fixer is still good.