If you need an original dust cap fir your we555 driver see what this seller is expecting….

http://www.ebay.com/itm/Western-Electric-Original-Vintage-Dust-Cap-for-555-555W-Receiver-Horn-Speaker-/221375080171?pt=Vintage_Electronics_R2&hash=item338afba6eb

So maybe I should go and get the ones I have lying in the dust!

All fun…