Hi,
If it is signed Kosta then it is Kosta..... If it is signed RK then it is Royal Krona.

Målerås was part of the Royal Krona group 1975 - 1977.
The Royal Krona group: Skruf, Gullaskruf, Åseda, Björkshult and Målerås
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Royal Krona has been discussed earlier on GMB.
I remember that Ivo had a query some time back about "Royal Krona ladies".
http://www.glassmessages.com/index.php/topic,17360.msg100289.html#msg100289" One of them is signed (RK########MJ) and has the Royal Krona sticker - so
I know it is Matts Jonasson from 1975-1977. "
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The Kosta period is after Royal Krona but before Mats Jonasson took over Målerås in 1981.
So I still think this paperweight is by Mats Jonasson/Målerås (as part of the
Royal Krona group) and that it dates back to the mid 1970's.
regards,
Ingela