Does anyone - Eric maybe? - know the location of Gernsheim's Cello Sonata No. 3 in E minor? Sonata 2 is Op. 79, and No. 3 seems to have the Op. number of 87.
Presumably an allocation of an Opus implies it was published?
By no means. Lots and lots of works with opus numbers remain unpublished and in MS - and "publishing" does not necessarily mean "printing" either.
I have only ever seen the score of No. 1, Op. 12, in D minor, pub. in Mainz by Schott (n.d.).
The scan on IMSLP of the MS of No. 2 (which is in E minor) is given the opus no. 79, though the score clearly has Op. 78. Since this was scanned by the Staatsbibliothek zu Berlin there is a good chance that they also have the 3rd Cello sonata. Maybe we should ask.
Thank you, Gareth, for your informative response. I am on the way!