It sounds like you have a potentially valuable and interesting piece of art! Peter Sculthorpe was a well-known American artist known for his vibrant and lively paintings.
As for the value of your 1982 signed poster titled "Coachman’s Rest" from the Tricentennial series, it's important to note that the value of art can be influenced by various factors such as the artist's reputation, the rarity of the particular piece, its condition, and the current demand for the artist's work.
You can also look for similar works by Peter Sculthorpe that have been sold at auction or through art dealers to gauge the potential value of your piece. Online auction databases or art sales platforms can be helpful in this regard.
If you decide to share a photograph of the poster, I can help guide you on how to do that or provide further assistance based on any specific details you might provide about the artwork.
