Purchased second hand from Nashville, TN based Ital International. Originally operated in Belgium.

The Thunderbolt may have been built by S.D.C. and not S&MC as listed. In continuation of the previously mentioned sale by ITAL, an additional source reports a 1990 S.D.C. model in Europe was sold by ITAL in late 1998. The dates, location and seller all agree, but the manufacturer differs.
S.D.C. went bankrupt in late 1993. So if this is indeed the 1990 coaster, it would have to be a S.D.C. model as S&MC didn't exist at this time. Likewise, if it is a post 1993 model it would have been built by S&MC. A mistake has clearly been made here, just where is the question.