You know what, I figured it out.  I looked to see if there was anything
printed on the cable, and guess what:  "Solbourne Computer Inc".  I believe
that they manufactured some Sparc clones?  In any event, it's definitely a 3
BNC cable and not a 4 BNC.
- Alex
Alexandre Lag?e-Jacques
alexandre.laguejacques at 
gmail.com