Parksman,
There is one on Facebook Marketplace in Clinton TN. Here's the link.
https://www.facebook.com/marketplace/item/621000288561573/
Edit: Not mine. I've just had it bookmarked for a while.
paulm12,
Sorry, I don't have any manuals. I just stumbled on the two pictures of Shopmaster on Google Images and copied them. Keep us posted if you find more info.
It's a railroad spike puller. They are still available new here. The ad below is from 1904.
http://www.rrtoolsnsolutions.com/catalog/TrackTools16.asp#94