3 letter barrel code

[sreming]

I just picked up an 870 16 gauge. The barrel code is 3 letters.
EEW is on the barrel. The receiver serial number is 6 numbers then W. No prefix in from of receiver serial#. The rear
Stock is plain. No checkering with a hard plastic butt plate.
The front stock has slits cut vertically
E - Oct
E - I believe is 1958.
W - what is this third letter for. It doesn't match any of the year codes that I find in listings?

[BKinzey]

There are a couple of charts but I think they are more like guesstimations rather than definitive.

https://oldguns.net/sn_php/remdates.php

[hauntingselection]

I just picked up an 870 16 gauge. The barrel code is 3 letters.
EEW is on the barrel. The receiver serial number is 6 numbers then W. No prefix in from of receiver serial#. The rear
Stock is plain. No checkering with a hard plastic butt plate.
The front stock has slits cut vertically
E - Oct
E - I believe is 1958.
W - what is this third letter for. It doesn't match any of the year codes that I find in listings?

Thanks! I came across that chart too, but the third letter “W” is what’s throwing me off. I haven’t found a clear explanation for it yet.

[andrewnon]

I just picked up an 870 16 gauge. The barrel code is 3 letters.
EEW is on the barrel. The receiver serial number is 6 numbers then W. No prefix in from of receiver serial#. The rear
Stock is plain. No checkering with a hard plastic butt plate.
The front stock has slits cut vertically
E - Oct
E - I believe is 1958.
W - what is this third letter for. It doesn't match any of the year codes that I find in listings?

The first two letters do look like October 1958 under Remington's barrel date code system. The third letter (W) is generally an inspector or assembly mark, not part of the date.

A plain stock with a plastic buttplate and the grooved fore-end also fits what you'd expect on a late-1950s field-grade 870. If the barrel appears original to the gun, a 1958 manufacture date is certainly plausible.

If you can also post the barrel address and the complete serial number format (leaving off the last couple of digits if you prefer), that can help confirm whether the barrel and receiver are period-correct.