As Neuro knows, some L lenses no longer use the alpha-numeric code that once used and are using numbers only. It is not understood to be a date code. I wouldn't worry about it unless you got a dud of which those are few and far between.
If you are a CPS member you might want to register the lens in your account and 'maybe' if it was pre-owned you might get a notice that it is/was registered by another user. Not sure if this is a possibility with their software.
You're going to love that lens! Extremely sharp and smooth all in the right places.
5D3, 6D, 1D4, 16-35 2.8L ll, 50 1.2L, 50 1.4, 24-70 2.8L II, 135 F2.0L, 200 F2.8L ll, 70-200 2.8L II, 70-300L, 100-400L, 24 TSE L II, 85 1.2L II, 100 2.8L, ZEISS 100 2.0, ZE 50 2.0, ZE 35 2.0, ROKONON 35 1.4, SIGMA 35mm f1.4, SIGMA 85 f1.4, S110, S100, sony RX-100 and one big-a$$ bag