Origin of using "clocked" to mean "noticed"

The word "clocked" can be used to mean "noticed", as in:

Bob: I'm gonna park here a minute. Did you see any traffic wardens about.

Geoff: Actually, I clocked one down the road on my way up.

I'm not sure how widespread this term is, but it's very common here (The Midlands, UK).

I've always thought it a bit of a curious term. Can anyone suggest as to how this usage came about. It is something to do with "time" (i.e. "clocking" someone on a stopwatch)?

Solution 1:

The OED’s definition of the verb in this sense is ‘To watch or observe; to look at, notice. slang (orig. U.S.)’ and the earliest citation, from an American source, is dated 1942. At roughly the same time the verb is also first found as meaning ‘to punch in the face’. ‘Clock’ is first recorded as a noun meaning ‘the human face’ in 1923. 36 years later it is found as a noun meaning ‘a punch’.

We speak readily enough of the face of a clock, so I suppose the extension of ‘clock’ to mean a human face is not so very surprising.

Solution 2:

I've always thought of "clocking" something as becoming aware of the thing, similar to "having it on one's radar". It seemed to me to be related to clock positions:

https://en.wikipedia.org/wiki/Clock_position

So to "clock" something would be to get the thing on your metaphorical clock, i.e. to know where it was in relation to yourself. It's easy to imagine military/prison slang adopting terminology based on this concept.