Brand
Charles Beseler's company started in 1869 making magic lanterns, stereopticons and even inhalers, and by 1943 it was an audio-visual supplier to the military and to schools. It came to the darkroom in 1953 with the 45 Series enlarger, and the smaller 23C wasn't far behind. Beseler's 1980 brochure called the 23CII the standard of medium-format enlarging and quoted Modern Photography saying it was built like a bridge. For a while Beseler also imported Topcon cameras under its own name. The company now works out of Stroudsburg, Pennsylvania, and still builds the 23C III-XL, the 45MXT and the Printmaker there, mostly for school darkrooms. That's good news if you buy used. Lamps, lensboards, carriers and bellows for most Beseler enlargers are still sold, by Beseler itself and by authorized dealers like KHB Photografix.
6 models we cover.

Beseler
Medium format$310–$600 typical ask
27 on eBay
Beseler
Medium format$825–$1,125 typical ask
13 on eBay
Beseler
Medium format$500–$750 typical ask
4 on eBay
Beseler
Large format$2,575–$2,600 typical ask
2 on eBay
Beseler
Large formatWhat comes with it and what to check →
Beseler
Medium format$950–$950 typical ask
1 on eBay