A book on Washburn history by John Teagle notes this about the M-7SW - if indeed its the same model you are asking about:
A short lived reissue of the late-teens early 20's Lyon & Healy Style B was available for a short time in the early 80's, built with carved tops and backs. Called the Country Mandolin, the M7SW had a higher (model) number than the Jethro Burns models only because all the other numbers were being used. This is not to suggest that they were not nicely designed, having the two point asymetrical body shape of the old Washburn/Lyon&Healy A' and B's, and the sytlish peghead of the old B's and C's. The black binding and oval soundhole also reached back to the 20's as did the solid spruce and book matched solid maple.
The sales flyer for this model lists as features:
Country Mandolin M-7SW
Original extended cutaway design
Hand carved solid spruce top
Ebony fingerboard with pearl dot inlays
Adjustable compensated rosewood bridge
Washburn style headstock
Hand-carved curly maple back
Available in tobacco sunburst and grained brown
Picture shows it in a rectangular hard shell case. These are pretty rare models and most I have seen have been highly regarded by their owners. As I recall, the early 80’s Washburn Jethro Burns F-5 style mandos were Model numbered as M4, M5S (or SW) and M6S (or SW) – and M6SW was the high end model with hand carved solid spruce top, maple neck, rosewood fingerboard and bridge, flamed AAA maple sides and back, and very cool “rope” purfling on the top edges. As noted above, the M7SW had a higher model number than the Jethro Burns F models only because all the other numbers were being used (the M2 and M3 were A style lower grade instruments). These Washburn mandos from the early 80’s era were made in Japan and were usually built with very good quality control and a thinner finish - as a result, they generally sound very nice with good tone and volume. I recall seeing one of these M7Sw's at shop a few years ago and I am pretty sure they wanted $700 or so – these retailed at $1200 new so one could have likely found one new for under $1000. Hope that helps.