Now and then I come across a coin like this. You really can't see it much if at all in the pictures, but I assure you it has substantial luster on the reverse but zilch on the obverse. The issue is known somewhat for lacking or having weak luster, but why do coins wind up with it on one side and not the other? I understand a little about how and why luster exists on mint coins, but what causes a lack of, or poor mint luster? Just asking for my own edification. This particular coin is graded AU50, has a much better strike than the usual for the issue - but luster on the obverse - nada.
When you get to the AU-50 grade, the luster is generally going to only be found in the protected areas. This particular coin appears to have significantly more wear on the obverse than the reverse does - hence, less luster. The reverse appears to be a higher grade AU, and the obverse looks more like EF (if I were to split grade it, I'd probably call it 45/55 - hence the AU-50 net grade). I'm guessing that this coin was displayed, carried, or stored in such a way that the obverse received more wear. And so, less luster on the obverse.
My guess wold be a substantial age/wear difference between the two dies. The original reverse died prematurely, and a new one was paired with the old obverse. That said, this is a low-mintage issue which could conceivably have been struck with a single die pair, two at most, so it does leave me wondering a bit in the absence of any actual knowledge of the specific coin.
Luster is created by the metal of the planchet coming into contact with the surface of the dies and then flowing across, literally being pushed across, the surface of the dies by pressure during the strike. And the more the metal flows the better, the higher, the quality of the luster. Less flow results in lower quality of luster. So, if the dies are spaced a tiny bit too far apart in the press, or if one is angled a tiny bit, or both are angled a tiny bit, or if the strike pressure is just a bit too low, then the resulting coin will have low or poor quality luster. Also, if any portion or given area of the planchet metal does not come into contact with the surface of the die and flow across it during the strike, there will be no luster in that portion or given area of the coin. This is typically seen in what we describe as weakly struck coins. The areas or portions of the devices that are weakly stuck simply do not have any, or at best very poor quality luster. Given that, luster, once it is created, is by its very nature, fragile. You might even say very fragile. It can be disturbed by even the slightest contact with virtually anything, and it can be broken or even destroyed by more than slight contact, or repeated contact - with virtually anything. And that is the result of what I explained above. For the same reasons I explained above. Even freshly struck some coins can have better luster on one side than the other, for those reasons. But it is also not at all unusual for one side of a coin to come into repeated contact with something while the other side does not. So a coin like what you have can be because of one thing or a combination of all of those things I described above.
From my research of the varieties seen in Heritiage sales for the last 15 years or so, there seem to have been two obverse and two reverse dies used in at least 3 combinations. This one is a type 2, which has the best of both dies - strongest details for obv and rev and also is the least often seen of the 3 identified varieties. I know the details are weaker on one side or the other of the other varieties, and there's a good chance the luster is weaker too - given the reputation of the issue. The likely factors so well described by GDJMSP! To know if the weak luster on the obverse is the result of mint factors or contact with "virtually anything" I guess I would have to see in person a number of variety 2 coins in high AU or mint state - highly unlikely I suppose! DUK
