The four 1.5 inch weights are all Vasart (or perhaps could be early Strathearn after the change of company name). They are of a size that were used on Bar Set pieces, or other utility items such as car gear lever knobs. They are also found as ordinary weights - I have an example with a Vasart label.
The weight with the Pirelli label is also a Vasart piece but just marketed through the Pirelli outlet. I think Frank has mentioned this elsewhere. As yet, we are not sure whether the Pirelli marketing was also used during the early years of Strathearn.