Validity and Authenticity of 6 ruble Russian Empire platinum coin overdate

I have been fortunate enough to acquire a 6 Ruble platinum specimen from the Russian empire and it turns out to be a graded overdate specimen that is graded AU-55 by NGC. I have only read of 1 such example of a platinum Russian empire coin being an overdate and as such I am curious to the authenticity and validity of this coin. The coin was purchased from Heritage Auctions. 

I have attached pictures of the coin to my message. 

1830 date is clearly visible. What would be the other date?

1830 had highest mintage for all platinum 6 rubles.

If you doubt authenticity, you can discuss it with NGC and HA

It’s an 1830/29 overdate, you can see the 2 under neath the 3 the 9 is trickier to see.

tokul

1830 date is clearly visible. What would be the other date?

 

1830 had highest mintage for all platinum 6 rubles.

 

If you doubt authenticity, you can discuss it with NGC and HA

It’s an 1830/29 overdate, you can see the 2 underneath the 3 the 9 is trickier to see.