S. Vietnam - 50 Dong 1975 - RARE!

I ran across this photo of a very rare coin of the State of South Vietnam. This 50 Dong piece of 1975 was made in large numbers (>1 M), but all but a few were melted. I hope to update the hammer price but with 2 days to go it's at better than $3k. This would be the obstacle in attempting to assemble a complete type set of this short lived political state, all the other coins are obtainable.