There are just two of these, 634c, known (as of 2013).

The image above is a 634c. If you compare it closely with your example, you will find that the spacing between the stamps or in your case, stamp and part of stamp is different. The white space between the real 634c is more narrow. Yours and the two currently offered examples similar to yours, but used (wishing for about $50 each from the sellers) on
ebay are from booklet panes which were slight miscut. The real 634c was made from stamps internal to a sheet, not the booklet plate layout.
Now to go with the illustration for Siegel's here is the description from sale #1040 Lot 2018 (dates 3/26-28/2013)
Quote:
2c Carmine, Ty. I, Horizontal Pair, Imperforate Between (634c). Bright color, crisp impression, trivial natural inclusion between stamps, light vertical crease between stamps resulting in tiny break at bottom perf hole
VERY FINE APPEARANCE. AN EXTREMELY RARE ORIGINAL-GUM PAIR OF THE 2-CENT CARMINE TYPE I WHICH IS IMPERFORATE BETWEEN. THIS IS THE FIRST WE HAVE OFFERED SINCE KEEPING COMPUTERIZED RECORDS.
Our computerized records, which include our Rarities sales from 1964 and all auctions after 1995, did not contain another example. A review of almost 800 PDF catalogues at our website found only one other. The Datz book states the quantity known as "very rare". A search of the P.F.'s online records located one other example (ex 1968 Lilly sale, described as unique).
With copy of 1977 P.F. certificate
Edited to add a missing "ed" to a word.