This was listed in the 2006 JNDA catalogue. Roy, would you happen to have images of such coins side by side? I don't know what the original "4" looks like so it makes it difficult to compare.
The difference is in the calligraphy of the character "yon" ("4") in the date. Although Krause calls the variety "large 4", there really is no significant difference in the overall size of the character. The drawing on page 25 of the current JNDA catalog (p.27 in the 2006 Ed.) shows the difference quite clearly. Normal calligraphy has small arcs on both upper inside corners of a rectangular box. The variety has a large square in the upper right corner, and a diagonal line almost reaching the bottom at the upper left corner. Unfortunately, I don't have an example of what the JNDA calls Variety A to photograph - it's very much on my want list, as the only copper sen I am missing. The catalog value is a significant multiple of the normal date variety. The shape of the character is very distinctive on that variety, and can be compared with the same character on any Japanese, Chinese or Korean milled coin dated 4, 14, etc.
