Ah, these! They are fascinating, aren't they. They appear in all four of the fruit patterns (I have nappies in Apple & Cherry, Grapevine, and Strawberry), and I've been told they have been seen in full berry sets (masters + 6 nappies). There's some controversy over whether these are Crown or not. They're from different moulds - note that they lack the fruit pattern on the base. The effect is nearly opalescent - if you hold them to the light, you can see the fire. They could have been a special order or a brief experiment, or they could have been the model for the Crown version. I don't know which.
Maybe some of the other pressed glass enthusiasts might recognise the pattern? If no-one does, then perhaps that's evidence for them being Australian. For the moment, it's a mystery.
Sorry about the delay! I'm just into the final months of my studies now, and what with the holidays and all it's been a bit busy.