Developing old Plus-X film

1. How much longer should I develop the film? I was thinking about an extra 40% or 14 minutes in Dilution H at 68 F? Does that sound reasonable?
2. Would using dilution B, make a difference with older film?
3. Is it better to use a colder or warmer temperature to reduce fog?
4. Plus X from this time period was still ASA 125, right? There is no film speed marking on the film canister.

Mike Wilde said:

You want a warm temp to battle fog, which builds with time in development. I would go with B if using HC-110 for the old film, and do a 'clip test' i.e develop about 2-3 frames (yes, you may end up cutting a frame mid way). I would start with at least 50% over the recommended time. If you have any pot bromide to suppress fog it may help, but will be a general restrainer and will force longer development times.

There are sites of guys who process found film that might have more details.

I have some mid 60's 120 ferrania pan that has long been frozen; it started life at about 100iso, and now acts like it is 12-25 iso. To get a good 'prints on grade 2' neg I develop it at d-76 full strength 20C for 18'. A contemporary plus x developer in this situation would be something betweeen 6 and 8 minutes. So don't be shy about extending developer times.

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