I agree with Derek. Vasart 1956 to 1964.
See the section on Basal Features in my page on Vasart / Strathearn
, which shows 6 weights in my "wide grinding" sub-section, three of which have the labels (Vasart / Pirelli) from that period.
But don't take everything I say in my pages as being a certainty! For instance, although I have not updated the details for one particular weight
, a friend has told me of a very, very similar example which has a Perthshire Paperweight label - so I might go back to my first thoughts on that one!