Some Schick Krona razors have the word 'Schick' on one silo door and the word 'Krona' on the other door. Some have the word 'Schick' on both silo doors. Some have no words on the silo doors. They all look the same when looking at them on websites (I don't own one) apart from some have a black tipped handle and some a metal tipped handle. Is there any other difference? Are there any known production years for the different words used on the silo doors? Thanks!