Certainly not all Sabino is signed, particularly earlier pieces, though I don't immediately recognise your item as a Sabino pattern. Certainly a number of firms produced opalescent glass in this style.
Regarding the mounts, I too have seen a number of bowls with this metal rim, etc., both floral designs like yours and a design consisting of 3 birds. Interestingly all have turned up in the US. I wonder if they were added by an importer or retailer? I also recall seeing mould blown vases with similar innappropriate mounts.
I quite agree with Ivo about the kitsch mismatch of styles; the metal mount really detracts from the item, while it might have originally been sold like this, it is deeply unfashionable now and I feel that the bowl would sell much better without it.