But I still question condition of 150 year old wood chips (not as easy to dig up compared to a lead bullet and steel items from the ground).

My guess unless you buy a chip have carbon dating done to the chip and you can determine what type of wood the chip is made of (and if the wood can be found in the area) would i be convinced it's the real McCoy.

I know of a private German WWII Museum in North Carolina (owned by an expert on the subject) who has a set of clay Swastika Chips, and claims they are authentic chips made for German Service Men. I explained to my friend who texted me the picture of the chips that they were made in the United States and really didn't have anything to do with Germany during WWII. Of course the chips could had made their way to Germany been found along with other WWII stuff years later, would that make the legitimate?