I've had these valves for years and always considered them to be some useless ex-mil types. I'd never find a use for them.
However, I checked out the details of them and in fact they'll be of use someday.
The AR8 is a 2volt double-diode triode and is similar to the Mazda HL23DD.
the ARP12 is a 2volt vari-mu pentode and is similar to the Mazda VP23.
Both have the Mazda Octal base.
www.radiomuseum.org/tubes/tube_arp12.html
www.radiomuseum.org/tubes/tube_ar8.html
The ARP12 has a Mullard look about it. The date or production code on the base is definitely Mullard style. A valve with a Mazda Octal base made by Mullard.
DFWB.