I'm no expert OP, but I know that in WW2 when 1903s and 1917 Enfields were refurbished, the smiths would just grab a good part they needed from the bin and install it, no thought was given to matching years and manufacturers.
Lets say your receiver is a '39. Lets further speculate that it had a rough looking bore, smith grabs a 1913 barrel, puts it on. It happened all the time.
Although you are correct, the one does look slightly odd and a 1912 receiver could very well have originally had a 1913 barrel. If you're really worried, take it to an expert. There is no way to tell for sure over the net.
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