This is indeed MOST interesting !!!
and thank you Fernando for the links to these earlier discussions, which I had completely forgotten. With those I can remember where I had seen these stamped markings.
I have been reviewing this and searching for more than a few hours since yesterday, and have not found anything among makers marks, trademarks etc. which corresponds closely enough to accurately assess these unusual markings. What seems clear of course, is that the same configuration of letters occurs situated in the same blade location on atypically mounted swords. This suggests the blades were in secondary markets or remounted locally using trade blades.
What I mean by secondary markets refers to the discussion earlier with Mark Eley's briquet last year, where I had mentioned the arms dealer mogul, Francus Bannerman of New York, and his phenomenal arms business. After the Civil War he acquired tens of thousands of US cavalry sabres, and I believe actually resupplied them to the army during the Spanish American war. He purchased huge volumes of surplus weapons and piles of captured 'bring backs' from this war and many occupations and campaigns.
It is believed he actually fueled a great deal of the arms collecting fervor in this country, and when he saw the demand for antique arms grow, he did begin fabricating interesting examples for the market. He actually cast hilts and placed stamps on blades, and I have seen many swords of latter 19th c. stamped with his name, with one dealer actually claiming Bannerman was a maker in Germany!
The reason I was compelled to think of Bannerman in those earlier discussions on Mark's briquet was that the color of the highly polished cast hilt seemed more red than most of these I have seen, and seemed incongruent with the older blade. Also the blade was hollow ground fullered, inconsistant as well with briquets, even with the many variations internationally seen. With these unusual cold stamped markings, placed longitudinally in the middle of the blade, it seems plausible that this might be a Bannerman product. While he stamped his name on many of his products, perhaps those of his family who also participated might have used this as some type of inventory code?
These letter markings seem commercially oriented, and with the block letters and serifs, and with underlined superscript lower case letters seem very antiquarian and suggest 19th century style, certainly England or the Continent. It was common even earlier to use this style in abbreviating names such as William, Joseph, with lower case second letter above the line of the first. Also, in the numero sign, the letter N in large block letter is followed by a small O underlined and above in the same manner.
The underline also often used in abbreviating Mc for Mac in Scottish names
Another subtle feature which causes me to think of Bannerman is the last group of letters, the two raised letters underlined seem to be TL rather than the TI originally thought. This may be an abbreviation for 'castle'. One of the most notable eccentricities of the Bannerman dynasty is that he actually constructed a Scottish style castle on a small island in the middle of the Hudson River in New York. Here he housed a huge arsenal and probably carried out much of his creative arms furbishing. Perhaps these stamped markings might allude there?
With that speculation raised, these markings may well be abbreviations as originally, and rather more plausibly suggested, a warranted type epigram which was commercially placed on trade blades in Europe. I have not seen this particular format or placement on British swords, but with the advent of industrial commercialism in the 19th century, it is not to say that similar stampings used on sundry metalwork might not have been employed for blades in the trade market.
These are my ideas, and I hope others might join in to see if we can solve this mystery once and for all!
It is a weapons forensics and detection challenge, so please join in!!
All the best,
Jim