You comment caused me to go check if the crown is signed. It is not, so it is nice to know that doesn't mean it is a replacement, by definition.Nice looking Seiko WT. I have one of those too, but with red 24 hr hand (6117-6010). Thinking of selling it fairly soon though.
BTW, some have posted that the crown not being signed with an 'S' means that it's been replaced. Not so, I bought mine new in 1969 (mfg '68) and the stem is not signed and is still the original crown.