I have this MacBook Pro with OS X El Capitan, and I'm using a LG 20M35 (19", 1600x900) as external monitor. This one has a VGA connection, so I bought a Belkin VGA to Thunderbolt adapter.
At first, it detected the monitor as a generic display of 13.9" and 1024x768. Looking for a solution, one week ago, I installed Display Maestro 2 without any different result.
Yesterday I tried to install a second external monitor using the HDMI port. I couldn't make it work, but for some reason, something that I did trying different things, the first external monitor (that I didn't disconnected from the MacBook) was detected as expected! I could see the first one as LG 20M35 monitor with its right resolution (1600x900).
Anyway, today, the monitor is detected as a generic display again. I tried everything to make OS X detected the monitor as an LG 20M35 but I couldn't. Could you help me please?