you can also look up "Merrow Machine" Merrow invented the overlock and began producing machines (for industrial use) in the 1880's. Their first machine was a crochet machine, then the three thread serger.
I am looking for an EARLY version (should be a 4 or low 5 digit serial number) so I can add one to the collection.
The earliest ones were clearly set up for treadle and then converted to motor driven. The design has not really changed since, so I hope to have a treadle serger eventually.
(Singer made one too, but I am not sure of the model # yet.)