I've got some rust on my 3rd valve. At least it looks like rust...is this normal? The valve is working fine, but I'm afraid it could cause problems in the future. This is a '73 Getzen Eterna Severinsen Model. The rust is mainly on the bottom outside, but there is some on the inside of one of the air holes. Here are some pictures. Any thoughts, comments, snide remarks, suggestions, etc would be appreciated.