Well, I do not think you can get the "90mm Elmarit-M" for that kind of money.
Elmarit-M is the term for the 90mm that went out of production in 2008 or so, and it fetches higher prices. A lot can be said about Ken Rockwell, but the info table here
http://www.kenrockwell.com/leica/90mm-lenses.htm#intro goes a long way towards clearing up the maze of different Leica 90mm lenses over time.
Possibly you can get one of the Tele-Elmarits for the price above, but I would say that the true bargain is the 90mm Elmarit ("first version" which was built from 1959 to 74. It is the one with the "ring" of leatherette on the lens barrel, near the focus mount. Forum wisdom
🙂 has it that is is sharper and less prone to flare than the later Tele-Elmarits. Build quality is exemplary. It is somehow unfavored and put down because it is the longest of the 90mm f2.8 lenses, and with the hood attached I do admit it looks a bit weird and Pinocchio-like on a Leica M
🙂 But hey, the pictures are great.
300 Euro guarantee you to find a very nice one in Europe, with caps and shade.
Greetings, Ljós