@alexandercoins, rarity is a relative thing. You are right that there were 10,000 of these minted. In trolling around vcoins and elsewhere, I see the similarly-designed 1/2 rupee coins for sale, but not the 1 pice. Purely in terms of mintages, those are 5x to 20x more common and I think that this is consistent with the fact that there are some readily for sale. In looking at the prices in Krause, I see that your bronze coin has a 2x value over a similar silver 1/2 rupee . Interestingly, your coin is dated 1928, but was actually minted in 1931 and those half-rupees (also dated 1928) were minted in 1929, 1951, and 1955. These two facts (the lower mintage and the higher retail value) suggest to me that your coin is a little more rare than other coins that circulated in Bhutan in the mid-20th century. Super-rare? I thin knot, but yes a little rare.
Regardless, it is a nice coin from a place that most of us will never visit.
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz