I'm figuring this is late 1960s. It came with my SCM Classic 12 which was built before the switch to a long tabulator bar on the 12" carriage models.
This is from the early to mid-1970s, off of my SCM Smith-Corona Galaxie XII.
My first non-typecast blog post except for my very first one that is now deleted. A few more scans from these two SCMs are coming up in the future. :)