The scope is much later than the rifle. It was made in the 1960s – 70s, likely by Schmidt & Bender. WEKU was a trademark of a distributer in Braunfels, a town near Wetzlar, a center of German optical industry. (New Braunfels in Texas was founded in 1845 by Prince Carl of Solms – Braunfels). Schmidt & Bender started in 1957, making scopes "for the trade" at first. These early S&B scopes are of quite good quality, optically far better than contemporary American scopes. Allen head screws came into use on EAW made mount parts at the same time.
The rifle was certainly refinished quite recently. Originally the receivers of these Haenels were case hardened, read the catalog description. The service load marking on the receiver ring and the corners of the receiver bridge seems to be "washed" by enthusiastic use of a buffing wheel. It reads: 1.5 gramm = 23 gr GewehrBlättchenPulver = (smokeless military) rifle flake powder / Kupfermantelgeschoss = copper jacket bullet. The glossy stock finish also looks "American" to me.
But it is still a very rare and nice rifle. At least it escaped conversion to a more available chambering. Ken Waters published many loads for a .25 Remington in 1973. The Haenel 1909 action is certainly much stronger than the American autoloaders and punp actions by Remington, Standard or Stevens. Alas, the Haenel 1909 was available in 6.5x57, 7x57, 8x57I, 9x57, 9.3x62 and 10.75x68 too.
Take the rifle apart and look for the proofmarks under the barrel. These may allow to narrow down the dating of the rifle: If the bore/land (not groove/bullet) diameter is marked with the old gauge number 313, it was proofed 1909 – 1911. If it is marked as 6.3 mm, it was made 1912 to 1914. Production ended soon after WW1 started August 1914, though some rifles were assembled from left over parts to the 1920s.