I apologize if this has been discussed before...I tried searching but didn't find this particular question...I downloaded a Singer 115 manual from 1915 and one from much later based on style of manual. The newer manual has no date, but says 115 in numerous places in the manual. It has the Stitch length adjuster like the 15-91's and 201's. But the tension dial looks like a Singer 66's with no numbers and in the position of 66. I've never seen any form of a 15 or 115 that didn't have the tension dial on the nose plate. Please educate me.
Btw. I was amused to see the error in the older manual that tells you to remove the bobbin with your left hand but clearly pictures a right hand removing it, lol!