I got this coin not long ago for very little. It looks to be ordinary currency but in hand is so sharply struck that it appears specimen. Well here is my semi-sorrowful pictures: I really would have thought the pressure relief of no collar would have dispersed the impact of strike and given more mushy details to the devices.
The opposite is true - with no collar, there's no pressure in the planchet to counteract that of the die, so it'll get more deeply struck.
Hmmm, my thick head does not follow - why would there more detail being struck up if metal is flowing away from the strike?
They struck 78 million that year, so maybe you have an EDS. Here is my 1964 in a mint package of some sort. Rough planchet on the obverse bust shoulder and center of reverse where the center rigging meets the gunwale makes this probably an average strike...
Really wonderful design, simple but a bit of elegance. The reverse edges/rims almost prooflike however on yours, I like it!!
Back to the point of dispersing pressures - the denticles show that on this coin, and the Blakesly (sp?) effect might be coming into play??
The Blakesley come into play when an incomplete planchet is struck. I don't believe that it is associated with off center or broad struck coins.
But it is the general principle that I was addressing - the relief of local striking pressure by adjacent structural defect lending to a "softening" of strike detail.
I don't know the answer. An incomplete planchet has a void and renders a weakness just opposite the void. This is more likely to cause a tilt in the die, (don't quote me). A broad struck and most that I see are very well hammered. On a centered broad strike you tend to have some stretching of the perimeter devices but the coin has great details. EX.
Hmm. 1964 appears to be a year in which the mint didn't cover itself in glory. I've got this error from the same year. About 5mm high at the widest point.
Let's see if I can describe this correctly. Because there is no opposing pressure from the collar to counteract pressure from the hammer die. Resulting in all the hammer die pressure being forced on the coin metal and into the dies' devices.
But the metal is "retreating" AWAY from the strike itself (in the event of no collar) and so would certainly think there to be a softening of detail as with the example of the Blakesley effect.