Answer: We are happy you enjoy our catalogs. OGH stands for “Old Green Holder” and OH stands for “Old Holder.” Over the years the third party grading services PCGS and NGC have changed the plastic “slabs” the coins are encapsulated in. In the first few generations of PCGS holder the paper insert that listed the coin’s date, grade, denomination, and serial number was green as compared to the blue insert they use today. The old NGC slabs were thicker and had a smaller hologram on the reverse of the slab. We use this notation in our catalogs to indicate to potential bidders when the coins were graded.