6A is a British designation
6A/1377 is a simillar model gauge but for 90 gallons marked.
have a look at
SpitfireSpares.com - warbird Instruments
About 1/2 way down there is a 110 gallon Lanc gauge marked to 90 gallons.
These guys are the bomb when it comes to parts and should be able to identify it for you. Let us know what you find out.