Use of very as an adjective is (in my experience) most frequently attested in phrases like
...the very person I was looking for.
To use adjective very with the indefinite article sounds quite bizarre in this case:
?...a very person I was looking for.
But consider this sentence, where indefinite a is used:
Visualizing a very transformation of the master-slave relation, Thomas presses further: the slave is brother to the master, even doubly a brother.
OED treats the two uses as separate senses of the word, with the following definitions:
(first use): With limitation (usually expressed by the or a possessive) to particular instances
(second use): Really or truly entitled to the name or designation
Here are two respective examples quoted in OED:
What would you say to me now, and I were your verie, verie Rosalind? (1616)
Thence we went into Queen Mary's room, and saw that beautiful portrait—that very queen and very woman. (1857)
Clearly, the difference in meaning between the two senses is quite light, and it seems to me like a kind of difference which is recurrent enough to have its own term. What is the proper term? Are there other English words having similarly related pairs of senses? And lastly, is OED jumping the gun in treating these as two senses? Could the difference in meaning instead be due to the choice of determiner?