Finding marks other than disks and intersection stations:
If you are looking for a non-disk item such as a bolt in a drill hole:
Be sure to read the entire datasheet carefully. Sometimes an older type of mark will be replaced by a disk but the datasheet will still indicate the older type of mark in the Marker Type or MARKER field. If the type of mark has officially changed, the change will be noted in one of the recovery reports, and the new type described in that recovery report. If there is no change in the type of mark indicated in any of the recovery reports, you must not assume a change in the type of mark and it will be as indicated in the Marker Type or MARKER field of the datasheet.
If you find a disk instead of the item described in the datasheet, you have not found the correct mark. In such a case, it is very likely that another agency who used to use the former mark has monumented a disk there. The disk is not a find.
If you find a metal nail, rivet, spike, and it is not exactly what is described then you have not found the correct marker.