If they do not say "non-corrosive" on the box, then I would not chance them. Cleaning the barrel with hot, soapy water three days in a row works to get corrosive primer residue out of the barrel. 

The earliest REM-UMC non-corosive primers that I have shot were in a box with a green, red and white plaid design. They were 6 1/2 primers and shot very well in my .22 Hornet; but I could never find their replacement.

Redsetter, good choice. One of the worst issues of Corrosive Primers is that they contaminate the Brass and it cannot be cleaned. The long term affect is brass that may break back at the Head. You can clean the barrel but the Brass is permanently impregnated. HTH regards, FITZ.

Primers of the vintage of .25-20SS production were likely corrosive, or mercuric, or, in rare cases, both.  In any case, it's prudent practice to treat any reloads produced by strangers as components only.

In the Dark Age before they started being available again, I found some fired Remington .32-40 HV cases and thought my ship had finally come in.  Reportedly, it was nice, heavy brass that would last forever loaded to target levels.

They went through the preliminary full-length sizing fine.  On shooting a few of them, I had a head separation, which halted the program while I cobbled up a broken shell extractor and got the rest of the case out.  There had been no shiny ring near the base or other evidence of headspace stretching, so on a whim, I tried to crush the broken case with pliers and it broke like porcelain.  All the fired ones did the same.  The cases had been fired with mercuric primers and were brittle and useless.

Rework, at least, was easy.  I snapped the loaded rounds like string beans or asparagus, poured out the powder, carefully pushed my good primers out of the bases, and threw the bullet ends into the lead pot for remelting.

I was thoroughly disappointed with that episode, but would have been heartbroken if they'd been .25-20SS shells, which in those days were much harder to find.

Primers, those "red and green" boxes were made in several varieties of load, and may well have various primers. Like most here have been saying just dismantle them and save the cases. Or, as I would do, just save the whole and start a collection of old ammo- plenty of other ways to come up with .32-40 hulls nowadays.

Just looked at the ".22 boxes" website to get an idea of when the "Rem-UMC" marking was in use, and on .22 ammo at least, the dates given were 1911 to 1920.  Earliest use of non-corrosive priming was 1927.