The ebay listing says 420vDC but the data sheet says 420vAC. The data sheet says metalized but does not say what is metalized - polyester, polypropylene, dried snot, kleenex, who knows?! The maximum 5kHz frequency makes me suspect it might not be polypropylene - not clear why you "now know it is ..."?!
Sorry, I'm just a suspicious SOB. It's cheap, give it a try - the worst that can happen is a blown fuse, and a REAL Bottlehead buys them by the gross at Costco! :^)