Any recommendations for particular editions of Georg Christoph Wagenseil: Concerto for Alto trombone and Piano? I've heard there is a PDF on IMSLP, manuscript perhaps, but I cannot locate it; This would be helpful as to develop my own interpretation (versus an edited one) and would likely be in the public domain and free—another plus. Thanks for any help!

You can find two different manuscript solo parts reproduced in Jason L. OLIVER, The Creation of a Performance Edition of the Georg Christoph Wagenseil Concerto for Trombone [...], University of North Texas (DMA), 2010. The manuscript of the orchestral parts are not available online as far as I know, and the cost of obtaining a microfilm or scan of that from the archive that holds it was pretty expensive last I heard.

Editions : there's one from Universal Edition, one by Alain Trudel, one from Cherry Classics edited by Ralph Sauer, on from Mark Reift. Haven't seen them all so I can't vouch for the quality of the piano reduction. The solo part you can always check against the manuscript to see what is original and what is editorial.