The two Vainberg sinfoniettas are op.  41 in d minor (which a cursory
memory of a skim of the score suggests is for small orchestra) and op.
74 (I think; http://ovar.myweb.nl/vainberg.htm also gives op.  70 -
conflicting sources? Has anyone seen a score?) in g minor for strings
and timpani.

The Miaskovskii sinfoniettas (the two I've heard- the better-known ones
for string orchestra alone- I, anyhow, like) are op.  10 in A major for
orchestra (unrecorded as of this writing, full or small but not strings
only!) (which I've seen in the collected works edition published some
decades ago), one movement of which (according to a page at the same site)
is an arrangement of a piano piece, op.  32/2 in b minor for strings, and
op.  68 in a minor for strings.  While Raff's sinfonietta was likely first,
was Gouvy's second?

-Eric Schissel