I work on a lot of late 19th and early 20th century guitars, many of them 'catalog'-type i.e. mass-produced, often not on the level of a Martin or Washburn .. so I know them pretty well inside and out.
I pulled these frets from an old L&H 'Lakeside' (c 1915-ish) the other day and noted that I rarely noticed this type of barb arrangement. It appears the ends were barbed, and the middle left un-barbed, although some appear to have a hint of barbs on them.
So my questions, have others seen this? ..what was the purpose? ..or was it just poor machining? (although the consistency of the pattern suggests intentional).
Those frets where not machined with barbs. They have been distressed by hand with a small sharp chisel or the like. I have no idea when frets started having a holding feature, barbs, manufactured into the wire.
What Paul said. I've seen lots of 19th Century mandolin and guitar frets that were barbed by hand like that; often much more randomly.
Some of the early frets had a kind of "knurling" or a series of machine-produced dents in the bottom of the tang to widen it a bit for better grip. Others may have been hit on the bottom of the tang with sharp chisels, producing diagonal barbs that stick out sideways.
The barbed frets as we know them today were first developed by Horton-Angell in 1929. Martin started using them, giving up the bar frets shortly thereafter - 1934 or so.
That's all good information, thanks! Yes, the frets in my pic, when examined, surely have a 'hand-hit' look to them.