The numbering on the dial is T3 24423 02 then 304933 01 I've had a good old Google but cant find anything useful

The wires seem to be original so I'm guessing the colours are too but I cant find any marking at all on the back of the gauge, I would be most grateful for any help.
One more question, I've done what a few people have done and cut a piece of plate to mount the gauges in behind the glove box outer trim (simlar to Theo's) - but how is this held in place? I could probable cobble something together but don't want to re-invent the wheel so to speak.
Thanks in advance.