Nothing special, the size was always aproximate, tolerance 2 cm was always accepted.
Yours one, however, looks a bit unsymetrical, so seems to me that your piece had not been accepted for selling, excluded, but stolen by some from workers and sold or given as gift out of official distribution.
Tons of glass had dissapeared from Skrdlovice glasswork every year (this info comes from former director of Skrdlovice glassworks Jaroslav Svoboda). Do nothing unique or an special design.
Sorry about it.