Lovely looking car Mark. Hess and Einhart did some early rag tops and I think some others did a version too before the original soft tops came out. Looking at the row of popper buttons you have on the rear of the roof it looks like yours is possibly one of the rarer pre factory jobs. There may be some sort of ID plate Hiding somewhere on your car stating which company was responsible for the conversion. I don’t think this makes any difference to the value but makes it more interesting.