Forgotten Weapons posted this on their social media feed. It was sent in by a reader who took it at a Swiss gun show. The handgun is a Mauser Model 1910 in 7.65mm, with what appears to be a custom gunsmithing job that mounted an early handheld light to the frame of the handgun. In addition it appears to have an extended magazine inserted, or a fixed magazine to convert the handgun into a single shot magazine as one of the commenters on the picture said. This same handgun appears on a European website listing it for 3,500 CHF.
The history of small arms is one of plateaus and timing. More often than not, a designer or a company will come up with a solution to a problem that just wasn’t ready for the era in which it came out in. However further down the line, when industry and technology developed, the solution was perfectly tenable. Sometimes the opposite happens and a solution is put forth that is just a little too late. This is true for any number of designs through the history of small arms. Projects such as the OICW, caseless ammunition are perfect examples. Although very forward thinking, the timing just wasn’t right because developments in other sectors hadn’t caught up. At the dawn of the 20th Century electronics and light manufacturing wasn’t able to put forth a light small enough as to not be obtrusive when using the handgun.