I've had a 10-ER for years. It makes a fair lathe, a fair drill press, and a horizontal boring machine, if you replace the shaft brake dogs with some made from brass. It makes the scariest table saw that I've ever used, and I only tried doing that once. It does make a horizontal boring machine, but the table height adjustment of the table is a bit crude and doesn't hold position well. It's supposed to make a 1/2" shaft shaper, another scary feature that runs at too low a speed to work well, so I never tried it, but I have the shaper spindle adapter.
The replacement brass brake dogs were made for me by a machinist son who copied the best of the originals. Another source would be any machine shop, but they won't be cheap. Why they made these of cast aluminum is a long lost secret that didn't work well. Brass is grabby when pressed against steel, so it works much better. You really need these to be able to lock the head and carriage to the pipe rails. The original aluminum brakes just don't hold. It isn't even a good drill press or lathe if you can't keep the head and carriage from sliding on the pipe rails.
The 10-ER was built by Magnus tool and sold it from 1947 to 1950. In about 1950 the newly formed Shop Smith Co. bought all of the rights to it and then completely redesigned it into the Shop Smiths of today. Nothing, except purchased parts not made by Magnus, like the power switch, motor, belt, and pulleys are still available for it, unless sourced from the local machine shop.
If you like to tinker with old tools and willing to live with it's lack of spare parts and shortcomings, it's probably worth $50. They sold new for $150 in 1948-1949.
Somewhere I have the manual and parts list, but it's a photocopy. I even have a woodworking book that was offered for it and this book is an original that came with my 10-ER.
Charley