I have only seen one 10.75 x57, and that on an 1888 Comm. Action sporter. Full length stock, semi-octagon barrel, lots of horn embellishment. HUGE price compared to most '88 sporters. It sold though.
But not to me. I would love to own one in this caliber. It was not spoken well of by Taylor, but he wrote poorly about almost all German calibers and rifles. I have read they were fairly popular with German influenced colonies and countries in Pre-WWII Africa.