I was asking if BOL's reached extinction(crashed and trashed)before TOL's, possibly due to lesser quality materials used. ? I may be off , but that's why I'm asking. I didn't consider whether they were produced at the same time or spanned by some period of time. If I've learned something hanging out here, it's that BOL units may(?) have as much longevity as the TOL's, and are separated only in features and hence, price?