Shop King Circular saw attachment

[Ken W.]

I got this Shop King circular saw attachment at an estate sale today. I really didn't want this ,but I saved it from the scrap yard. It's dirty but still turns. Any idea of how old this thing is ? 

[Bill Houghton]

If it's the same company, maybe this would help: http://www.vintagemachinery.org/mfgindex/detail.aspx?id=745&tab=3