1903 Barrel with "A" under date

[Tul8202]

Need help in the meaning of the letter A that is underneath the barrel marked as follows:
S A
(flaming bomb)
05
A

I appears to be a 30-03 converted to 30-06 but have yet to know for sure what the "A" means.

Any ideas?

Information

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[Mike D]

The "A" was stamped on the barrels of rifles that passed through inspection, if the barrel was "acceptable", or still serviceable.

[John Beard]

Adding to what Mike D stated. Rifles turned into Springfield Armory for overhaul prior to WWI were inspected upon receipt. If the barrel was deemed to be sufficiently serviceable for re-issue, an "A" was stamped beneath the barrel date.

Hope this helps. Happy New Year!

J.B.