I don't know how else to phrase this question, but I stumbled upon a file which I know from the header is gzipped (1F8B0800) but I am unable to recreate the file no matter what I try (including gzip on OSX, gzip on Linux, compress, and zlib). Even weirder, the gzip -1 output of the gunzipped input is smaller than the input. And weirder still, I see some plaintext (like PNG headers) at near the 80% of the file (followed by more of what I believe is compressed data). I don't think it's unrelated data though because gunzip doesn't give the "trailing garbage ignored" message.
I guess my question is that is there some older version of gzip that gives an output that is larger than a modern gzip -1?