Thank you Mike and Chris. That's a lot of detail.
As I said, I am a total newbie to guns, so I have the least idea of what NPB means. It was mentioned in one of the handwritten papers related to this revolver.
BTW, is the price of this revolve really as low as $200 - $300 in the USA? This is not first-hand information but I heard from our neighbour that my Father-in-law was offered an equivalent of $1,200 about 4 years ago. It is probably because guns are not in use as much here in India as in the USA.
Now that I have more information, thanks to you guys, I shall check the local gun store about the pricing.
Thanks, once again!