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I received many responses to my question on the GF status of A-1 sauce.
The consensus is that it is GF.  I still wanted to confirm so I called
Nabisco.  They said that it is on their GF list but I persisted to
question the carmel color and the vinager.  The nutritionist finally got
back to me. She could only say that those were both from artificial
sources.  I pressed for the source - especially the vinager.  She said
that it was a food grade alcohol NOT FROM GRAIN.  That is all she could
disclose because that is what her suppliers disclose.  She insisted that
the product is GF.

That's the best I could do.