Here is a facsimile edition off the original manuscript as originally set forth for Eb trumpet, with the original marks.
To quote the web site, "This is part of the Paul Handke manuscript. Handke was a trumpeter from Vienna who moved to the United States and became first trumpet in the Philadelphia Orchestra (1901 - 1903). He then played first trumpet in the Chicago Symphony Orchestra (1903 -1912).
He wrote the solo trumpet part (in 1899) from the authentic and original manuscript by J. Haydn. The work was not brought to public attention at that time (Handke only kept it as his personal copy)."
With this particular transcription, you can do the old trick of substituting bass clef for treble clef, adding the accidentals, and playing it on tuba to your heart's content:
http://abel.hive.no/trumpet/haydn/handke.html
I downloaded it for myself. I'll probably never work it up to full recital quality, but it's fun to tinker with on occasion.