I expect the +4+ is the one built by Rutter in the 2000’s using the spare factory shell and a new chassis or maybe there where 2 shells that were completed.
It might be on the money at that guide given it is non original and built from parts must hit the value of it.
Does look very nice though. I wonder what the are like to drive as they would still have the ladder chassis, king pins and leaf springs. Evidently the issue with the SLRs. Is that the body cracks as the chassis flexes but the body doesn’t., expect it might be the same issue for the +4+..
Will