There is bound to be lots of these still kicking about.
I have been purchasing ex Royal Navy lamps for my conversions. Most have been what appears to be virtually unused blue MF type. I did try charging the odd one up and testing it, best burn time I could get was 8 hours.
I remove the plates for scrap and keep the casings, you would be surprised how the weight of lead adds up and not far to go to sell here in central England.
The best lead acids I ever had where the old T2s, the last I bought was the T6 which was rubbish. National Battery Company of South Africa rebranded.
Just a thought, John E if you read this. Was there any markings on the packaging of the one you bought that could indicate ex Royal Navy. Its usually a load of bar codes and some markings like "Land DMC" "Sea DMC2", Contract No etc
My avatar is a poor likeness.