The Martin Handcraft
The "Handcraft" models were handmade and hand engraved instruments that were produced for a very long time.
The Handcraft introduced bevelled toneholes to the US (Cousenon was probably the first company with pseudo-bevelled toneholes) and Martin tinkered with them considerably throughout their history. Of all the Martins currently in my possession, a Handcraft C melody, a Handcraft Bb soprano, a Pedler Martin-stencil alto, a Handcraft Troubador alto and a Magna tenor, none have exactly the same style of toneholes.
Some horns feature the name of the craftsman that assembled the horn engraved someplace either on the body or under an altissimo key.
Finally, I've seen a ton of documentation recently that the basses from Martin are actually Conn/Buescher stencils. The tone holes are distinctly different, so I agree with this assumption.