That's very interesting: I speculated that perhaps Ravenhead was one possible manufacturer and a photo of the two glasses side by side would add some weight to this.
I'm not sure of how long Ravenhead produced their 'Slim Jim', but I believe the Swirl decoration was dropped in the mid-1960s. Robbo also noted quality differences between some glasses and this does lend some credence to the possibility that Chance did change glassware supplier (or Ravenhead improved their production!) at some stage. I have a photo of some Swirl decorated glassware that does appear to be on good quality glass - see brandy balloon on '
http://Shapes' page - but it's difficult to assess without having the item in front of me.
You said that Chance had simplified the Calypto design for smaller items. How about changing this to the Calypto design was modified to suit Ravenhead's machine-printing process?
A very strong possibility; for Chance's slumpware the enamel was firstly applied to the blank sheet of glass, reheated (which 'fixed' the enamel) and then slumped. I was a little stumped (and slumped) when I first approached this subject, but how they decorated the Handkerchief vases was a big clue – silk-screen printing's not that good!
But it would make sense that with Ravenhead producing glasses and having the ability to decorate them, why create problems by increasing extra levels of production for yourself?
Also I presume that the gold rim was heat-fixed for permanence.
I can't be certain, although it is reasonable to assume as the enamel was fixed in this way. The gilt on the rim had to be finished by hand so this would either have been applied to the blanks before or after slumping. Some pieces of Fiestaware also seem to have far shinier rims but this could just be associated to slight wear and/or aging. Perhaps even how they were stored or displayed?
But the good news is that, according to the Centre when I enquired about speaking to a 1960s factory worker; "oh, there are tons of 'em"!
So, it looks to me as if I have a fine set of Ravenhead glasses, made to a Chance specification and design, which were shipped to Chance just for labelling, boxing, warehousing and distribution.
A strong possibility that could still be answered by Ravenhead.
With regard to works records from Chance, apparently Pilkington have these at St. Helens all boxed up and access has always been denied in the past... but I can ask.