Macromedia licensed the MP3 technology in 1995 to use in their Shockwave product. .SWA or Shockwave Audio was originally added as a free plugin (Xtras) to SoundEdit 16 to export AIFF files to .SWA.
.SWA files have the same structure as MP3 files but with padding at the beginning of the file. Samples show the hex values
00 00 01 40 00 00 00 03 00 00 for the first 10 bytes. No ID3 tags obviously.