They're professional quality. I found multiple google results, still sold today. I have no idea if being old would change the value or not. Also found this:
Product Features5.0" Classic Levelset shear by Yasaka. Made of stainless steel produced from Swedish Sponge Iron. This iron is made with iron ore containing an extremely small amount of impurities. The resulting steel has a low impurities content and excellent wear resistance, and is a fully rust proof stainless steel. All classic levelset and offset shear handles are replacable.Yasaka shears were first introduced to US hairdressers by the visionary, Geri Cusenza, founder of Sebastian International, over 30 years ago. Hundreds of thousands of Yasaka shears were sold, and they became the standard for function and affordability. Unique in their two-part design, each shear is a combination of Japanese forging techniques, modern machining methods, and traditional hand-craftsmanship. The result is a shear whose design continues unchanged to this day, with many of those original shears still in use and beloved by their owners. Blade - Semi Convex Edge Handle - Classic Levelset Tension - Flat ScrewFinish - Brush Size - 5.0 Metal - 5 Star
So there's tons out there but they're of premium quality. You can either list them for what others on the auction site has them at or cut somebody wanting a pair a little break and hopefully sell them quicker. Good luck.
Will be uploading some pictures of these I don't know much about them. Would like to know there age I'm guessing there older than all the other s-50's listed online because mine are different they don't have ridges on the handles would like to know there value plan on listing them on ebay this week.