Dating the scope is exactly that and could have nothing to do with the year the rifle was made. It could have been installed at anytime and putting a newer or older scope on a rifle could have been done for any number of reasons. Same goes for the barrel, it could have been installed anytime after the invention of the specific cartridge. Finding out the actual PO Improved cartridge will give you the earliest possible date of change of the barrel, but it could also be anytime after that as well.
Maybe start with a chamber cast to determine the cartridge. Also, there could be markings that are not visible because of the stock that would be helpful. It's not like your client has to worry about buggering up the screw heads at this point. Might as well take it apart.
Determine if it's a wall hanger or is safe to shoot with modern ammo and go from there. Looks like it would be a hell of a nice rifle to take to Africa for PG. Best of luck to your client.
EDIT - Check out the second rifle on this thread I found. Looks like a FN action similar to yours. I couldn't post a link. I copied the text...
Yet another German bolt action rifle - the Schmidt & Habermann Modell 21
When it comes to pre-WWII German bolt-action rifles, everyone thinks "Mauser", but there were others too, but all less successful and consequently much less frequently encountered. We have already described the Haenel models 1900 and 1909. Now it's time to turn to another Suhl made full-bore bolt action: the Schmidt & Habermann Modell 1921.
The venerable company E. Schmidt & Habermann of Suhl was founded in 1860. During the 1920s it was owned by the brothers Franz and Paul Stadelmann. About 1930 Schmidt & Habermann offered the usual complete program of hunting guns from cheap hammer shotguns to sidelocks, drillings and combination guns of all descriptions and even over-unders, some of their offerings undoubtedly bought in. A reprint of one of their catalogs, even with English descriptions, is available through the GGCA bookshop, number R024. One of the S&H trademarks was "Waldlaeufer" = woodsloafer which term now generally describes a special type of drilling, essentially a side-by-side shotgun with a small bore, .22lr or .22 Winchester aka 5.6x36R Vierling barrel inside the top rib, used then for off-season, year round fox and rabbit hunting, the small rifle barrel intended to give a little more reach just in case.. As Schmidt & Habermann did a lot of work for the trade, you rarely find a gun openly marked by them, but if you inspect the guns of the countless country and city gunmakers, even "named" ones, closely, you may sometimes find their "ESHA" mark hidden inside. Recently I have seen an "Original Wilhelm Brenecke Leipzig" 7x64 M98 bolt action rifle with the S&H stamp underneath the barrel.
During WWI, all the Thuringian gunmakers were occupied with making stuff for the German army, either complete arms such as pistols or at least some parts like those for the Star-marked M98 rifles. So when the war ended in 1918, Suhl was full of M98 parts but without work anymore. Hard times befell all the German gunmakers then: No more military orders, the restrictions of the Versailles treaty, international trade restrictions and economy coming to a downslide, resulting in an inflation that got to its peak in 1923, when a loaf of bread cost several billion Mark. Very few people could afford new sporting guns. Gunmakers tried to survive by converting ex-military M98 actions into affordable hunting rifles. Schmidt & Habermann offered these too, as did all others. Everyone tried to invent a product that would allow him to survive in some market niche. Immediately after WWI Mauser was out of the commercial repeating rifle market, the Haenel rifles were gone too, so the Stadelmanns decided to offer an "improved" Mauser-type hunting rifle. Due to the loss of Germany's African colonies, little need was seen for a new magnum length action. With all those reworkable M98 actions floating around, it made little sense to compete with them. The main rifle quarry of German hunters then was the small roebuck. Many hunters then felt the standard-length Mauser cartridges like 8x57, a prohibited cartridge anyhow, or its "Ersatz", the 8x60, much too destructive for those tiny deer, so S&H decided to offer an "Improved version of the short Mauser K action, chambered for the then-popular short roe-class cartridges 6.5x54 Mauser, 8x51 and a new, now forgotten 7x54. Later they added the .250-3000 and the 5.6x52R aka .22 Savage High Power to their offering.
S&H designed a simplified, small ring, round-bottomed K-length receiver without a thumb-hole cut, but with sort of a "square bridge" on the receiver ring to provide extra steel to cut the usual claw-mount dovetail in. The bolt assembly was also simplified, falling back on some pre-98 design features. The guide-rib on the bolt body is omitted, as is a third or safety locking lug. The firing pin lacks the post-1902 front safety lugs too.
The unique bolt sleeve and safety arrangement is completely different from the Mauser design. Instead of a flag safety to block the firing pin there is an arrangement that allows the rifle to be manually uncocked to set it on "safe".
On their M21 S&H employed a big "Cocking Knob" on the firing pin nut, similar to those on the American Krags and Springfields, but rather unusual on German full-bore rifles. A spring-loaded latch is set into a slot in the right side of this knob. If you want to set the rifle on "safe", you grab the knob with the left hand, depressing the rear end of the lever latch with the thumb, pull the trigger and lower the firing pin until the protruding forward end of the latch rests against the bolt sleeve. Now the gun is on safe with the firing pin tip held back from the primer. Pulling back the firing pin recocks the rifle, the latch snaps back and allows the firing pin to go fully forward on firing. This arrangement looks quite good at first glance, but it is not very comforting to work it with cold fingers and under a low-mounted scope, so Schmidt & Habermann followed popular demand and added a Greener-type trigger -blocking safety as a factory option.
Apparently the Schmidt & Habermann Modell21 was not a real success in the market, certainly caused by the costs to make them. Though the action was much simplified , the 1928 Akah catalog showed a price of Reichsmark 240.- for the basic version, RM 40.- more expensive than the superior original Mauser K-actioned sporter!
When I have the rifle in hand, I will post more about it.
