It's clearly an amateur change to the original marked aperture on the lens cell, likely from an ignorant person who either replaced the shutter or found it as-is and decided to "fix" the mismatching numbers, but didn't understand how apertures and f/stop scales work. Probably saw that when set to f/6.3 it was wide-open and so changed the f/4.5 marking to that.
Post #3 surmised the shutter was from a 14" f/6.3. I don't know what else there is to add. It's obviously not a factory change, at least from what I can see on your blurry photo.
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