If I remember corectly Seidelmann was a New Jersey sail maker. In the 1970''s he produced an interesting little 25 footer. They were clearly designed as race boats and did acceptably well on the race course because they were intended as rule beaters. These early boats were reasonably well built but by any objective standard were tender and especially well rounded.
Seidelmann expanded their line fairly quickly and with this growth the design and build quality really seemed to go down hill. Seidelmanns quickly developed a very poor reputation. The later boats that I have been around were clearly very poorly put together.
That said, if you have had your boat surveyed and it was found to be in solid condition, and you are pleased with the way the boat looks and sails then that is what counts. I would avoid putting too much into the boat as their reputation would tend to limit resale prices even if the boat was in premium condition. I am sorry that I don''t have better news.