Long ago Buck Knives did have a true custom shop, you could order most anything and there were craftsman that could make it. It no longer exists.
Today, as I understand it, those marked custom are special runs, but go thru the production line. The 118 I posted is marked custom and has 5160 steel...special run for Copper and Clad. The ones that we can order with special scales, blades and steel are also marked custom. Hopefully they get special attention but are made on the production line.
There are craftsmen at Buck Knives today capable of custom work and do produce build outs. I know Joe Houser along with his regular duties makes one offs of different models, a 184 Buckmaster blade, mirror polished with an elk antler handle comes to mind. He also did the 'Black Widow' 119. HTH, Preston