Made in Czechoslovakia
According to the research that we conducted regarding the glass floats marked 'Made in Czechoslovakia', there is no particular glassworks to be mentioned as the producer, but the most interesting fact is that due to custom law (export regulations) all the glassware meant for export had to be marked or stamped with 'Made in Czechoslovakia'. Here is a quote from the 'Glasmarken Lexikon' source:
'Markings Made in Czechoslovakia, Czechoslovakia, Tchecoslovaquie and similar ones, partly with the company name or product name and often the statement of size e.g. 3/8 (toll) can be found on many Czech companies' glassware from 1918'.Czech made glass floats that we came across were three-piece molded and sized as 5,6,8 and 10 inches in diameter. The location of the marking is on top of glass. The marking is of 2 variations - the circular writing and writing put in two straight lines.
Colors we have seen with this marking are of dark green, olive green, ruby red, cobalt blue, amber, aquamarin and crabbery.

A 'Made in Czechoslovakia' marked
olive colored glass float. Sized as 5 inches in diameter. From our
own collection.

Beautiful cobalt blue colored czech glass float. The picture was kindly provided by Richard, a collector from the US. Now resides in Olav's collection, Oslo.

'Made in Czechoslovakia' glass floats. Ruby red and olive green colors. Sized 5 and 8 inches in diameter. The picture was provided by Richard, a collector from the US.

Amber colored czech float. The photo was provided by Richard, a collector from the US.

A honey colored 5 inch glass float marked 'Made in Czechoslovakia'. Was used for fishing in the North of Norway. From our own collection.

An aqua colored 6,5 inch glass float marked 'Made in Czechoslovakia'.
From Tom Rizzo's collection.

Honey-amber and green 5 inch floats marked 'Made in Czechoslovakia'.
Reside in a private collection in Oslo.