In the rear of the power booster I can spot a quarter sized flap of loose rubber around the pushrod. I believe it broke off of the main portion of some kind of rubbery seal. Is this seal important or just a dust cover of some kind? To replace it, is this available in the aftermarket, can we adapt another rubber thingy, fabricate something, or is it maybe included in a rebuild kit? As I understand it, the '59-'60 Cadillac models use the same booster. Sorry for all the fotos (the second foto is the best), it's really difficult to see back inside there. I remember having one heck of a time removing/replacing it when it was rebuilt some years back. Thank you.