I always think of Oldhams as "black battery", "clear battery" and "red battery"
The black ones were ex-NCB and typically good for 4 to 6 hours' main beam, but cavers all carried carbide lamps and just lived with it.
The red ones often had vent plugs made from biro end-plugs and a twist of wire, because cave water isn't good for battery cells! Hard-core cavers had hybrid lamps made from assorted headsets fitted to red batteries -
real hard-core ones had lamps made from ancient Youle or Wolf lamps with ex-WD NiFe cells inserted! These gave a light not unlike a candle in a brown glass bottle. Note that this was pronounced "knife", not "ni-fee" in those days.
The clear batteries were often the first new lamps a caver owned. Biro-end vent plugs were still in fashion - remember to take them out when charging!
They don't make em like that any more..... just as well, really. Now I have a Chinese thing like a tiny yellow box, lamp flex up over the crown in vintage style, and it suits me because it gets nil maintenance and seems quite unaffected
plus ca change, plus c'est le meme chose