Unfortunately, L&N manuals aren't the easiest to come by, I have manuals for only a few L&N instruments, the old double ratio bridge is one of them I don't have. I do have a manual for the 4235 Wheatstone bridge, this one had handles on it and I think it was good for 0.03% basic accuracy and also went up to 1111 Megohms. Unless some idiot has really damaged these old bridges, they are still very good for their age and pretty stable as long as they were not overloaded severely. I will look around and see if I can find any other old manuals in my archives when I get a chance. Outside of the switches being damaged beyond repair (and not having a junker to cannibalize), most of the resistors can be fairly easily replaced if needed although the low ohms are a bit harder to make.
I have an old Rubicon Wheatstone bridge in a wooden case, used to have an optical galvo for the output (another wooden box) but I didn't get it. I have an old Rubicon very low ohm bridge; the model 1600 low resistance standard with the 1610 double ratio box, they used to belong to the Navy years ago, quite a large and heavy beastie. The double ratio box was also missing the conical shorting plugs used to select the ranges (just like that other L&M double ratio I've got).