Neat assortment of mandrels. I have seen this tool for a number of different bayonets (even the Polish Wz24/27). In German use, they would likely have been part of the Gross Waffenmeister repair kit, or found in a larger, rear echelon repair facility. I think when used, heat was likely applied to the dented area, to help the mandrel force back the metal. Once metal is bent or dented, it is also stretched. Thinner mil on a sheet sometimes has "memory", and can be popped back with minimal evidence of having been dented. The steel on a S84/98 T3 scabbard is surprisingly strong. In many instances it would take working with mandrel, metal hammer, & heat to reform. This often appears on refurbished scabbards, where evidence of hammering is seen. As for values, this ranges as to type, condition and markings. IMHO this could range from $100. up to $150.+. I have a couple very nice bayos with a crease in the scabbards. Have always wanted to see what improvement I might be able to make by use of a mandrel, but have yet get my hands on an example to try this out...