1x crown D4958-1 output stage insulator.
Fits sa2 and psa2. Sa2 was slightly wider due to thinner side panels and wider back panel. So if you have a psa2 you will need to carefully take about 4mm off each side of this insulator.
Made to replace dry burnt out sponge on early models.
Genuine crown part.
Rare as rocking horse poop!