WASHINGTON (AFP) - It's not bubbly-cute any more, but Treasury Secretary Jacob Lew's new official signature, to go on all new United States (US) banknotes, should meet boss President Barack Obama's admonition not to debase the currency.

Revealed by the Treasury Tuesday, Mr Lew's signature for the greenback still had some of the characteristic swirls that drew howls when he was first nominated in January.

But - thankfully to many - it was a far cry from the eight-loops-and-a-tail that he scribed on White House memos in his previous job as Mr Obama's chief of staff.

That signature brought a slew of good-natured ribbing when his nomination was announced, drawing more attention than Mr Lew's likely policy approach at the Treasury.

But it was important to some. For more Americans, the Treasury secretary is most familiar through his signature on US banknotes.

In his White House version, the stylish scribble starts off with large loops, narrows at the middle and then grows back to large circles at the end.

One graphologist described it as an "unraveled Slinky", and the name behind it is absolutely indecipherable.

That led Mr Obama, when he introduced Mr Lew as his Treasury pick on Jan 10, to say: "When this was highlighted yesterday in the press, I considered rescinding my offer to appoint him."

"Jack assures me that he is going to work to make at least one letter legible in order not to debase our currency should he be confirmed as Secretary of the Treasury."

The new version probably will allow him to keep the job - it looks like a signature rather than a doodle.

But someone who did not already know the Treasury chief's name would be hard-tested to identify it from a new one-dollar bill.