I think its optical illusion. Look at how the shadow of the light falls. If its embossed the light would be coming from the bottom. And the shadow falls the same for all the letters/numbers.
The stamping appears to be embossed. If you look at the first three numbers 892, you can see an accumulation of dirt in the hollows formed by the embossing. If that were a stamping, dirt would not accumulate in that manner. Just my opinion.
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