When I showed Beppe’s safety-pin tie clasp in two separate looks before it was always with a knit tie. Several people asked if it could be done only with a knit tie – well, I found another photo I hadn’t published and he is wearing his safety-pin with a wool (cashmere?) tie.
p.s. I bought a safety-pin tie clasp like this at Ralph Lauren for $10 – I also saw a silver version in Paris for $149 Euros.