I think yours is a Vapalux 21C.
Hi Martyn,
I think the '21C' is the WD/MOD number for the lantern. I think the Vapalux designation was M1
I believe the WD / MOD didn't like the revised globe shape of the Bialaddin 310 so asked for a modified frame to accept a 'standard' shaped globe ( as I guess they had a heap of the older style globes on store room shelves) So the M1 features most of the running gear of a Bialaddin 310 with a modified frame...( are you asleep yet??). Interestingly enough looks like the WD/MOD were right and now the 310 globes are no longer produced / available but you can get an adaptor plate to convert a 310 to a standard globe....
As you say they are cracking lanterns and I'd rather have 1 Vapalux / Bialaddin that 20 Tilleys or even a moden coleman.
Cheers
John