Solitude Productions' catalog numbers are usually formed, using the next scheme:
SP. NNN-YY - for CDs
SP. NNNLP - for vinyls
Where SP. is a label's name abbreviation (note, there is a space after the dot), NNN is a release ordinal number, YY are the last two digits of a release year and LP refers to LP album.
This doesn't apply to the first seven releases, where the "year part" was not yet introduced.
The release dates can be usually found on the official label's web page.