Do you think you are talking to the Antique Roadshow?
Artworks from Robert Sills Galleries are all actual real oil paintings by primarily unlisted artists. They not fakes or reproductions per se; the issue on the market is that the artists who painted the vast majority of the works sold through them just did not become famous or take-off on the secondary market (i.e. sell for profit). These sell primarily for decorative wall art purposes and they are not collected for fine art investment purposes. If you bought them direct from the Sills Galleries in 1980's, then the realistic expectation is that they will likely re-sell now for less than what was paid for them in the 1980s.
Please take a moment to leave a rating by clicking the stars. If you require further assistance, no worries, the question thread does not close even after leaving a rating.