Well, to add a bit more confusion...
Pieces that looked like Royo style glass were said to be imported by Ardalt from the Gordiola glassworks in Mallorca to the US in 1960-61. That seems very easy, BUT there was no mention that the pieces were signed Royo or Cire** (Cirere? Cirese?). From what a friend in Spain told me, the enamel on this 1960 glass was not as thick as the enamel we typically see on the Royo glass. So maybe the 1960 glass was a reproduction of an earlier Spanish glass? or maybe there were different qualities of glass exported to the different markets? It is hard to know for sure, because no one is 'fessing up.
One thing I think we can say with some degree of certainty is that the glass probably is from Spain. Maybe soon we can pin it all to Mallorca. The Arte Catalan we see on labels may simply refer to the style. (I think there was also a fine arts show of that name in Barcelona, wasn't there?)
Anita