When the hell did Johann Gutenberg "invent" the printing press?

I've got a clever little idea for the beginning of a paper I have to write, but I can't find one clear year for Gutenberg's "reinvention" of the printing press. I've seen from 1436 to 1453 (which I believe might actually be the year the Bible was first mass produced). Thoughts? Definitive answers? Complete wild guesses?

http://www.gutenberg.de/english/zeitgum.htm
It is only known that as of 1448 he had established himself once again in his hometown of Mainz. The first evidence of his presence dates to October 17, 1448 when he received a loan from his brother-in-law Arnold Gelthus.

It is not known whether Gutenberg had already established his printing workshop and now needed cash to carry on with it, or if he was in the process of establishing it. However, it can be assumed that a printing workshop was soon established in Mainz since only three and a half years later the massive project of printing the Bible was tackled. Long periods of preparation and testing must have preceded this phase during which the printing of smaller projects helped gain the necessary experience for this prestigious and successful venture.

It also has to be assumed that Gutenberg had to prove the viability of his new technique before he found new investors. His workshop mainly produced school books of Latin grammar for which a great demand guaranteed success.
The obviously well-planned new start in Mainz, the fact that Gutenberg quickly found coworkers with the required skills and abilities, and his convincing of Johannes Fust, a wealthy merchant and moneylender, to grant the credit for the Bible project, all indicate that Gutenberg was not only a man with long-term vision, but also an excellent organizer and a calculating business man. This is further fueled by the (unproved) assumption that he organized two workshops, one for quick sales and the other for the production of the long-term Bible project. Thus the image of the lonely, ascetic and abused inventor that was presented by writers of the 19th century and even some authors of this century, can hardly be maintained.

In the summer of 1449 Gutenberg received a loan of 800 florins from Fust for the preparation of printing equipment. The collateral for this loan was the equipment that was produced with this money. The workshop was established at Hof Humbrecht which belonged to a distant relative of Gutenberg’s who resided in Frankfurt.

In the years 1452 and 1453 Fust gave Gutenberg a total of another 800 florins for the production of books. With this capital investment the typesetting and printing of the Bible could commence. While the Bible was printed between 1453 and 1454, there were works of a very different nature printed as well in Gutenberg’s workshops.

One for the site, which surprisingly didn't come up in any of my searches, and one for not making any Steve Gutenberg jokes. :)

And I've been involved in print all my adult life.