My guess is whatever was least expensive that week. There are only three types. Knurled, Knurled with a split shaft and setscrew: round with a flat milled side for the setscrew to land on. performance wise, there's no difference There are a couple of other types but they wouldn't be on a bass. The majority of after market knobs are set screw type because they are universal. The split shaft type should have the slot filled to keep the screw from mashinng the slot closed. Sarge, have you ever thought of making your own? They are super easy to make if you have a good variable speed drill. The exotic wooden knobs are sky high, too. But they sure do look good. Matching knobs and pup covers would make a beater look good.
Sure. Give me a day or two and I'll shoot you PM with the info. It would make for a fairly long post and rather than shanghai Sarges post, I'll start a new thread if there is any interest.
When I replaced the knobs on the SX Jazz I bought, I went to www.basspartsresource.com and bought the "Import Jazz Knobs". They fit just fine.