When I bought them, I was thinking of that Egersund design too

They do have their stoppers, made from a red rubbery material, rather perished.
I can make out "SUBA SEAL" and a patent number (I think) "Pat No. 469982". Suba Seal seems to be a worldwide brand of rubber seals for everything, chemicals, medical things etc.
Judging by the stoppers they would appear to have at least some age to them. The unglazed base rims also have that grubby look.
Lynne I see what you mean about Rayware - check
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=120143883493