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The date codes are T3 and F4.

The T3 is definitely a factory stamp with all the other normal factory stamps.

The F4 looks to be hand inscribed with no other markings!

Dead men don't talk. :)

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Finally! I have found both the razors and the key to unlock them. I had put them in separate places.
It took me 3 days of looking to get them together again! :)
The key is inserted into the...