I think those are the plates off the bottom of in tank fuel pump. If you can bleed the air out of the filter bleeder valve they are from a old pump. If not they are from the current one and it will run but not pump.
Your not going to like the results of adding UMO to your diesel fuel. As posted elsewhere on Steel Soldiers, my experience was just like yours; poor performance, stuttering engine, problems with the filters getting plugged. Long term problems will most likely be damaged injectors & injector pump.
As mobileauto2000 stated, those are the bottom plates off an intank fuel pump. Hopefully, not your current one!