This high-end external speaker is designed to improve audio quality in shortwave radio reception, where good sound is frequently difficult to obtain.

A 1997 "Grove Enterprises" print advertisement promoted the SP-200A for "under $200". It is a box-like device with several knobs on the front panel.

There is also an SP-200 model; it's not clear how this is different, or if some references just leave out the "A". Searching for it on eBay will sometimes yield results.

According to NASWA.net, there is an improved 200B model as well. Apparently it appeared in a 1997 issue of the "Monitoring Times".