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Those part numbers indicate the specific assortment of attachments the box contains. Certain Singers were provided with boxes of attachments and the numbers can be traced to that model of machine.
Thanks, Joe. Can you tell me a website where I can start to research them? Thanks so much...
The Yahoo group "Singer-attachments" has a spreatsheet with a lot of information in their files section on the attachment sets and what machine they came with.
Sigh ......... I know what those numbers mean, but I can't remember where I saw them. Brand fade. I'll keep my eyes open and post the links when ( if ) I find them.
#160977 is on the box that came with my Singer 206k Swing Needle.
Info from Singer attachments in my collection.
#160623 = Singer class 301 machines
#160809 = Singer 15-91