Hello Dmitry. Yes, this one is still a mystery, as both forms look extremely similar and perhaps the naval pattern went on to become the mountaineer sword. Besides the example of the ribbed iron-hilt listed in both of Gilkerson's books listed as "naval", there is another of the same pattern appearing in "Navies of the American Revolution" by Preston,Lyon and Batchlor. Until more is written on these types or unless the sword itself has provenance, I think this remains a fuzzy area.
If anyone has a copy of Boarders Away II out there and a scanner, the arms chest on pg 189 again has this sword stored away with other weapons. Could they send us the pic here to open the discussion further? This chest is also not clear as to where it was used, but Gilkerson does explain why he believed it to be naval.