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 ebuzz

Thanks, but there seems to be some disagreement as to whether they'll play at 33 or 45. Not a real big deal, I'll figure that out easy enough. As long as there are no issues with today's cartridges, but as Czarivey admonishes: I'll be careful.
To Mattmiller: Yes, they are pretty thick.
To Ghosthouse: You are correct, it should be a single "O" not Groovy!!
To Elizabeth: I think you are also correct. They may have been freebies b/c old authie did belong to a record club as some of her LPs state they're from the club.