Thanks very much for your responses!
BainDarret: B&H stated that if they said it is a dryfit, then it is a dryfit. They couldn't provide any more information/confirmation over the phone.
Ralph & Matt: The battery was not marked Nickel-Cadmium. And it didn't have any cap to replenish the electrolyte. So I took
the chance that it was a dryfit as advertised, and set the metal pin to Dry instead of Nicd or Pb.
It seems to have charged up OK. I left it overnight to charge and now it is working. While
charging red and green lights were on initially, and by morning the red light had gone off (which I assumed to mean it was >80% done).
I left the charger plugged in for about 6 hours more. I also cleaned the contacts
on the battery and the holder with a cloth - they were a bit grimy.
Recycle time is about 5 seconds after a flash discharge on full power.
Once again - thanks very much for the help.