Figuring out a substitute for an old amp capacitor - value and type
Just want to put it out there:

Here is a entry from a blog of Mullard Magic about TROPICAL FISH CAPACITORS. It contains the original information (with the voltage ratings and the full codes explanation) AND A TABLE OF ALL THE DIFFERENT TROPICAL FISH CAPACITORS MADE with their respective data:
http://www.mullardmagic.co.uk/blog/month/2012-5?pagenumber=2

Here is the datasheet of C280 series capacitors (aka tropical fish):
http://www.electrojumble.org/DATA/C280_Series.pdf