"About" as an adverb

[Cooklava]

About the only thing you can get for a nickel these days is five pennies.

What is the adverb about modifying? Is it modifying the adjective only or is it modifying the noun phrase "the only thing"?

One othe question, is the entire phrase "About the only thing" a noun phrase?

Thank you very much.

 

[susiedqq]

The only thing you can get for a nickel these days is about five pennies.

I moved the word to show that it is really acting as an adjective to tell "how much"