Definitely a US issue or mock up for the USA. Probably a mock up, as I can't find any evidence that Blues & Soul was issued exclusively in the States as opposed to the generic International edition.
The picture of Michael Jackson is the same as the one on the cover of issue #300. Some of the features (eg EWF, Poll Results are the same).
Unrelated to this "magazine" there is an album listed on Discogs "Celebrate Black Music Month 1980 - Sampler" which incidentally does not feature Michael Jackson or any of the artists listed on the front cover of this magazine/mock up.
I'm not sure how this fits in here as a UK issue of "Blues & Soul" from June 1980 ...
Unfortunately the resolution of the front cover image is only 560X420 so it is difficult to make out the detail ..... BUT ..... as far as I can make out ....
It has no "Issue Number" ... The UK "Blues & Soul" issues for June 1980 were #305 (3rd Jun 1980) and #306 (17th Jun 1980), with #307 being 1st July 1980.
As far as I can see the date is "June 1980" with no specific day mentioned.
It has a "Bar Code" ... they were in existence in 1980 but it wasn't until some years later that they became universally used in The UK.
The price isn't right ... "Blues & Soul" was sold for 50p in mid-1980 ... the price on this issue looks like it could be £1:25 ... or could that be a Dollar sign and $1:25??? Even as late as 1990 "Blues & Soul" sold for only £1.
The cover photo of Michael Jackson does look to be from his "Off The Wall" period and the other artists featured (Chaka Khan, Fatback, Brothers Johnson) were around at that same time so it does relate somehow to Mid-1980 or thereabouts.
So .... my theory is that this was some mock-up or special "retro" edition from some years later and possibly originated in The USA. .... do any other budding Sherlock Holmes out there have any further theories?
The magazine was contributed by "Doberman" of Minehead, Somerset, England, who doesn't seem to have been active for two years ... I wonder if he is still around to help us out?