@elfkin my partner/girlfriend and I just picked this Rex by Nakajima 345-2L up earlier today for her. She has a Brother embroidery/sewing machine, but needed something for more intensive applications like multiple layers of denim and nylon. She has been sewing for the last few hours since we set it up, and she loves it.
It came with the original manual, but we have not found much about it online besides it was probably made prior to Juki buying out the company in 1965.