Eyes, Preservation and Identification
Condition and taxonomy answer different questions. A preservation grade cannot establish a species or a quarry occurrence.
Describe what is preserved
A condition record should describe visible eyes, articulation, the head and tail shields, compression, breaks and any repair. Preparation and damage should be documented from the actual specimen.
A grade is not an identification
My grading describes condition; it is not a scientific taxonomic rank or evidence of rarity. Size, completeness and price do not determine species. The morphology of the actual fossil and its documented provenance are the relevant evidence.
Keep the taxonomy supported
Flexicalymene belongs to Calymenidae, not Dalmanitidae. The Mt. Orab reference documents F. retrorsa and Isotelus at genus level. It does not justify calling every Isotelus I. maximus or I. gigas, or transferring a species name to a specimen from a locality label alone.
Before buying
Review photographs of the actual specimen, its condition notes and the individual eBay listing.
Reference
Hunda, B. R., Hughes, N. C., & Flessa, K. W. (2006). Trilobite taphonomy and temporal resolution in the Mt. Orab Shale Bed (Upper Ordovician, Ohio, U.S.A.). PALAIOS, 21, 26–45.