There were two basic types: hard-wired and battery-powered. This one is battery operated and uses two of those big old six-volt batteries with the spring contacts on top:
I opened this up and discovered a nice paper labels that provides some details. Notice there are four types shown - the battery operated one, one for 110 volts AC, one for 115 volts DC and one for 230 volts DC. The battery-powered one is designated the Sym. No. 100.2 Portable model and you can find online a brand new one of these for sale for $98 under that model number. This label also shows an "FSN" or Federal Stock Number which would date this particular battle lantern to the 1960's. What is interesting is that this one is gray, when it had been thought that by the 60's they were all yellow. It may well be that the label was added to an older lantern during repair or rehab.
Here's some more of the inside:
The lamps look a bit like a headlight from an old six-volt Volkswagen: I can imagine these wore the batteries down rather quickly. A pair of these batteries today runs close to $20 with tax so I resisted temptation to put in a fresh set and see how long they lasted.
On the back is a bracket to attach it to bulkhead brackets.


































