This is a Scott # 300-311, Part-Set of 12, Mixed Mint & Used; the 300-308 are all mint OG (LH-HR); the 309-311 are used; most are bright and well centered. Common terms/abbreviations: mint=never cancelled; OG=original gum; condition of OG: NH (never hinged), LH (light hinge mark), HR (hinge remnant), HH (multiple or unusually large hinge remnants); sound=no thins, tears, creases, stains, perf damage or alteration, significant fading, heavy pen or pencil marks on back, or other major faults (this excludes straight edges, poor centering, heavy cancels, or other problems clearly visible in the listing photo). Extensions of the return privilege are available, upon request, for those wishing to obtain PSE, PF, or APEX certifications.