this Mendelssohn recording I uploaded some weeks ago. This is not one of the works that made it into the Odyssey LP boxes that were discussed in comments to that post, though it did make it into a Biddulph CD set of the Budapest Quartet's Brahms recordings that appeared about 20 years ago - which, I imagine, is long out-of-print as well.
Brahms: String Quartet No. 2 in A Minor, Op. 51, No. 2
The Budapest String Quartet (Roisman-Schneider-Ipolyi-Schneider)
Recorded April 30 and May 1, 1935
Victor Musical Masterpiece set M-278, four 78-rpm records
Link (FLAC files, 85.53 MB)
Link (MP3 files, 49.35 MB)