Hi John,
The cartridge base you have is a 1 1/2" J Mk IV T illuminating cartridge. The bases were 'milled' for easy night time recognition like this:
Milled all round = Red.
1/2 Milled Circumference = White.
1/4 Milled Circumference = Yellow.
Unmilled Circumference = Green.
Hope this helps,
Regards, Ned.
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