I simply got curious and asked. Here is what I received from the Argentinian
chess federation as a reply:

Dear Sir:
Michael Greengard isn't included in our rating list (Ranking Argentino)

He probably played chess on line, obtaining another kind of rating.

Sincerely.

M. Z.

Again, many possibilities, but the Argentinian 2300 is looking more and more
bogus.....

Is this another George O'Leary case (for those with short memories, the coach
who falsified his resume for years and was not caught until hired by Notre
Dame.)?

In Mig's defense, he did put the rating on the line; he didn't withdraw from
the tournament ; and seems ready to prove he is a 2300. If so, a chess book
looms - do you know how many players would snap up a book that claimed to be
able to take them from 1700 to 2300?

Mig, it looks to me like you got caught but I love your writings so I hope you
find a way to turn this straw into gold..

I already have the title - The *Real* Chessmaster at any Age," given that the
author of "Chessmaster at Any Age" supposedly only became a master due to
fiddle points (something I never bothered to confirm, but the timing looks
accurate).

SBD