A few observations. The logo on their letter head is not the real logo of the medical center. Granted it could have changed since then, but typically companies / practices don't change their logo at a whim, because its something iconic that the public are familiar with and have a rapport with.
Perhaps the letter is fake and the intention is painting the scenario that MJ was Dr shopping for drugs?
And on the other hand it could be legitimate, home page of this place shows that they have a reputation for treating dancers, athletes, people of high profile, etc.
They are arthritic specialists with a focus on stem cell injections....
But yeah, the use of euphemisms such as This is It and You ain't seen nothing yet, are kinda mind blowing. I kinda tend to think this is from MJ and a mocked up letter, that he then leaked, and it is based on a Medical center he has been affiliated with or that he knew of so that it 'looks genuine'
Would have meant nothing at the time it was floated, but a lot once 'This is it' and 'hoax' were launched.