The company name was Riihimäen Lasi Oy well before 1988 - quick google in Finnish brought some reference to Riihimäen Lasi Oy from 1910. Ahlström Riihimäen Lasi Oy changed it's name to Karhulan Lasi Oy at some point. Today Karhulan Lasi Oy produces packing material out of glass for medical, food and brewery industry according to one recent document I found on the web. Karhulan Lasi Oy now belongs to Owens-Illinois, Inc.
According to book that I have, "Moderne Zeiten - Finnisches Glass 1929 -1999", Riihimäen Lasi ceased to produce studio glass (my translation for "in Handarbeit hergestelltem Glass") in 1976. I would guess that the reference to Riihimäen Lasi ceasing its operations in early 90's probably is meant to indicate that the company stopped producing any kind of decorative glass then (but couldn't really find any conclusive evidence, i.e. no full history recount of Riihimäen Lasi). I would also speculate that was when the name changed to ARL.