This coin is at least worth the silver it is made of. Some people enjoy collecting old coins,and I am one of them. I own coins from Anshubarma time, Malla dynasty and so on. I also happen to have Prithvi Narayan coins (and coins from all Shah kings). But you are right, if you are not into collecting the coins, it might not mean much. On the other hand, rarity is something very few people (with money, and appreciation for civilization) appreciate, and are willing to pay for. Imagine how many coins there are left from anshubarma or prithvi narayan era? So, these coins are worth at least some thing more than silver inherent in them. How much? we don't know. Demand and supply will determine.