...What, with my experience making these things being limited to a few months working with Eric, before he quit, but just at a guess, I'd say probably sometime after 1830?
It strikes me that most of the swordcanes out there fall into one of three rather hazily defined categories:
1. The "Gentleman's" swordcane--Usually shaped like the familiar crook-top or handled cane we are all familiar with. Usually has a thin blade, and is often meant only for thrusting.
2. The "Renaissance Walking Stick"--These are where the real artistry happens, most of the time. They can be any size or shape, and are often very intricate, both in decoration and operation. Hidden spring catches, spring-loaded spikes, and odd reservoirs or chambers are all reasonably common, here. Blades here tend to be more along the rapier or smallsword line, given the styles of the period.
3. And, finally, the "Stealth Weapon" sticks--These are where you get things like the Japanese Bankers Canes, the Zatoichi Stick, and the ever-popular 'Blind Fury.' Some other weapons get lumped into this category, too, although they may not necessarily be considered swordcanes, per se. I put things like the Bo-Yari and the dual-blade baton in this category. While it is not altogether impossible to find very nicely crafted and intricate examples of mechanisms and stylings in this form, most often the goal is to make the stick or cane look as commonplace and unassuming as is possible. To this end, you'll find odd-sized and bizarrely-shaped blades, fitted into gnarled and twisted shafts, a lot more often than in either of the previous two categories. And oftentimes, the fittings are simple friction-fit between the scabbard and blade, to ease not only construction, but also to hasten the draw.
My assumption, Gouge, is that you have a Group 1 piece. Possibly carried in Europe (where the bamboo swordcanes were very popular with the Colonial Brits, although practically any nation that traded abroad had at least a few of these types of things floating about), or from the Southern US (where many a Riverboat Gambler in New Orleans or 'Swamp Merchant' in Florida might have carried a surprise with them!). Once I see pics, I might be able to give you a better idea about it. That it has a Solingen Blade tends to make me think that it is more likely from the 20th century, since--if I remember from my time with Eric--it's been a lot more common this century to put 'other blades' (i.e., blades that started life as something else) into swordcanes. I don't know for sure, but I'd guess that Solingen didn't make that blade with the specific goal of it becoming a swordcane, but I could be wrong. I'll wait for the pics, before espousing any further theories, rather than make a real gaff, here.
Oh, and FullerH is right, you or your friend has a real nice display piece, there. If you choose to carry it on the street, and a nice Officer finds out that you have it, count on spending some time discovering the joys of our Legal system. These things are more illegal than an unregistered Class III AK-47 for the average Joe to carry. You can own it, collect it, or make one. Just be aware that if you're caught with one on the street...you're busted.
So don't get caught, okay?
Kal