from Crys at Needlebar regarding my G&B Lockstitch
"
I don't know what needle this model uses but G&B used 3 kinds of non-curved needles. So one of them should work in your machine. There is a flat shank needle known as the G&B 19. It is just about impossible to find and I don't know of any equivalents. It is 1 7/8 inches long and the flat part of the shank is very small. i.e. it's shankless. It's not much bigger than the shaft of the needle.
G&B also used 2 kinds of round shank needles. One is the 13x1 and the other is the 2x1. For the 2x1 you should be able to use LAx361."
I have put in a Boye #2 and it works great.
also, based on this serial number DB
http://fiddlebase.jimdo.com/american...-grover-baker/
(the webmaster says it was pulled from the digital copy of grace coopers book on the Smithsonian site)
mine which is serial number 340205 dates to 1871.