Up for sale here is this set of 4 NOS vintage Sprague Black Beauty 160P capacitors. Each is marked .25 uf 600v, and tests around .26-.265 uf, with minimal leakage/ESR.  These will work great at full voltage in an amp.  These have old price tags on them but they will probably come off easily.  Please see my pictures for details and test results.

US shipping and handling is $8, and international is $36. If you have any questions, please ask.

I have more capacitors and other vintage electronics listed--feel free to take a look!