The Writing Desk Reference Section: Vintage pen information
What does JM&Co mean on my Yard-O-Led pencil?
JM stands for Johnson Matthey and they used to make or assemble certain products for Yard-O-Led up to the 1960's. This is why some pens carried the JM&Co assay mark. During the 1960's Yard-O-Led bought the tooling from Johnson Matthey and started producing all the products themselves but JM continued supplying Yard-O-Led with silver tubing well into the 1980's.