What's the deal with Microgrove LPs?


I recently raided my girlfriend's elderly aunt's record collection and came away with a few 7" records labeled: "CBS Masterworks." They're from the 1950's and say they are
"microgrove" LP's, but nowhere does it say at what speed they play.
I can't tell if they're 45 or 33 1/3 or something else.
Has anyone heard of these and is there any issue with respect to today's needles?
The grooves do look very close together.
ebuzz

Showing 1 response by czarivey

7" of 50's are always 45rpm and there's no issue with current sound pickups. I'd be cautious about condition of these not to damage your speakers with loud clicks pops that may occur.