Hi James, I've looked through some old auction catalogues at home and examples with the full backpiece like yours are listed as "Danish mid 19th C" no pattern date I'm afraid. I agree the W could stand for Weyersberg, a Solingen firm that later made blades under contract for the British 1885 cavalry sword but my 85 has the mark Weyersberg, Kirschbaum & CiE Solingen on the forte.