Thanks to Deuce for an enjoyable and topical EV (the intersection of 23 and 43 is also - grimly - topical). The conclusion of the preamble, “there is one abbreviation in each of the initial and final grids”, might suggest that the abbreviation in the initial grid is missing from or altered in the final grid. But I don’t think that is so because one of my modifications to the initial grid (which included an abbreviation) require the initial abbreviation to remain in place.