It appears you probably have the standard (not super) 650. I am getting this information from sales records kept by Joyce Wilson (she and her husband owned a chainsaw shop). They kept records of every Homelite they sold by date, serial number and saw type. From a quick look, here is what I found:
16101273 - 02/76 - 650
16102119 - 02/76 - 650
16102120 - 05/76 - 650
16102116 - 07/76 - 650
16102122 - 08/76 - 650
16101273 - 10/76 - 650
46101345 - 09/76 - S-650
46101346 - 09/76 - S-650
It appears that they were two totally different serial number strings, but you can estimate your saw was most likely produced in 1975 from this. Here it the link where I got my info:
Wilson's Saw Shop - Sales Record - Homelite