I should have just asked Dela first... I swear you've had at least one of everything. 😊
So I went back down the rabbit-hole because I hadn't in a while... granted my main source is a little bit dated, but it's a very good source considering the guy who compiled it was working there.
According to the Gospel of Michael, there were 217 EB-28's built, and 874 EB-18's. There's also this mysterious column of 98 listed as Unidentified. Since they fall in this table that could be anything I guess. The EB line only lasted from '79-'83, and by the time they pulled the plug on these it probably didn't matter tracking them anymore. Maybe that's how this one ended up a fretless?
For what it's worth, they were completely different models. EB-18 was longer scale (33.825") set neck of mahogany into a maple body, with passive electronics. The EB-28 though, was a neck-through construction, (shorter scale 33.1625") contoured mahogany body with active electronics. Screw a chatbot... I'll take Mike's word.