Hi Frank,
The Hermanova 20034 attribution comes from the CGR 1962/8... the first time I believe the Matura ashtray appears in the periodical.
In subsequent editions, the Matura ashtray is referred to as 983/15cm Moravia-Rosice (CGR 1963/7) then 983/15cm Rosice (CGR 1963/12, 1965/3, 1970/3...). Always 15cm.
By the way, Mark Hill (Hi Sklo Lo Sklo) attributes the ashtray to Libochovice 983, and also (wrongly) gives 17cm as the diameter.