[Phlogiston]

Somebody probably replaced the filters before, but it doesn't really matter, either will work. The only real consideration is the maximum first filter rating for your rectifier tube - you have to look it up.

Here is the deal. If the first filter cap is too large it is like putting a short on the rectifier - well any cap is like putting a short on the rectifier - as it is being charged on power-up. The rectifier is rated to deal with this to a point and it is usually listed in the tube manual.