Duracell CRV3 batteries have 2 AA 3v lithium primaries in them... flat topped. I have 6 packages of them here and opened one of them. I got them hoping they were 1.5v instead but that is only the energizers.
I think only energizer uses 1.5v lithiums because they have the patent on them while the others have to use 3v ones.
before lithium AAs were more mainstream people would buy the CRV3 energizers and harvest the cells from them for cheaper.
I recently bought two two packs of walgreens CRV3 batteries (rebranded energizers) for $4 a pack and they had 1.5v lithiums with nipples in them all... black wrappers though. $1 for lithiums is a good thing.
I was once thinking about using these 3v lithium AAs in a UK 2AA light with a 4AA eled head.... shorter runtime but smaller form factor. I am guessing you could use them in a mag with the AA adapters and have twice the voltage to drive a brighter bulb till you ran out of cheap 3V AAs....