What am I bid? (structure)

According to a forum user the expression, seemingly always expressed as a question, gives the meaning:

"What am I bid!?" is an expression usually used by an auctioneer when he is starting a bidding process for an object that he is selling. He is asking for someone to offer a price (bid).
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There were two films with this name, one in 1919, and one in 1967 about a person who wants to become an auctioneer. The only place I've seen this in a dictionary is at Lexico, which gives the English->Spanish translation of:

  1. what am I bid for this vase? — ¿cuánto ofrecen por este jarrón? (Roughly "how much are you offering for this vase?")

The meaning is pretty clear, but I have two questions:

1.How should this sentence be parsed? For example, "bid" is a verb in "What do you bid?" and a noun in "What is your bid?" What is it, or was it, in this expression?

2.Can the expression be conjugated for grammatical person, as in:

What (are they/is he) bid (at the auction).


Solution 1:

"What am I bid?" (Please note that, in English, it is an error to have two punctuation marks together.)

This is a shortened form of "What amount of money am I bid by you for this item?" which is the passive form.

"What...am........I........bid?"

object verb subject past participle