An interesting coin for sure. Here are a few thoughts:
1) I would use considerable caution when drawing conclusions about coins that are (A)
overstruck on earlier coins (since the designs are often intermingled with one another) and (B) worn and/or dirty, making the details more difficult to see.
2) I absolutely agree that the top design is that of Nicephorus (the
overstrike) and that the
head shape doesn't match
his normal design at all, but rather looks very much like that of
Constantine VII (SB 1761).
3) The
reverse is where the overstriking is clearest, so that is where I started trying to decipher what coin(s) this one was struck over. I aligned the photos with the letters and below are the results (with drawings to support). We can see that the letter arrangements show clearly both the
reverse of
Nicephorus II (SB 1782 as you correctly discerned - drawn in light blue) and also that of
Constantine VII (SB 1761 - drawn in gold).
4) The fun
part is translating these areas to the same
part of the coin on the
obverse side - because we should see the same designs dominate the other
side in the same places on the coin (where the dies
had something to push against on the other
side). In other words, where the SB 1782 design dominates on the
reverse, the opposite
side should also be dominated by that
obverse design - the same being true for the SB 1761 design. Based on the contour of the
rim, I took a shot at translating the equivalent areas on the
obverse, using the same colors that were used to represent the 2 different designs on the
reverse. The photos are posted below.
5) What we see is that you were absolutely correct - a coin of Nicephorus with the effigy of
Constantine VII. However, it isn't because that is how the dies were made, but rather a fortunate
die alignment that nearly perfectly blends the 2 designs seamlessly together. It helps with the blending that they are both wearing
loros. A final
bit of confirmation is this: while the
obverse legend of both coins end with bASIL
ROM, where the letters fall relative to the
cross on the crown of the emperor is different. Coins of
Constantine VII have the
legend as bA + SIL while those of Nicephorus are arranged as b + ASIL. On this coin, we see that the arrangement is that of
Constantine VII.
6) The last photo I've enclosed is from a recent
auction (March 2021 - Savoca Coins 98th Blue
Auction, Lot 1947) that shows this design blending more acutely. At first, it looks like a new garment for
Christ on a
Class A1 coin. Instead, we are seeing the
bust of
Nicephorus II (SB 1783) up to about the lips of
Christ (note the design break) - and then the 'normal'
Class A1 design above that. On the
reverse, the
side opposite the
Nicephorus II design is the Nicephorus
reverse legend and the A1
legend is opposite the
head of
Christ - both as expected.
I
hope this is helpful.
Kevin