In my professional opinion, the following item is:

#308 Harrison. Side Plate Block of 6.   

I grade this item: Medium Fine 3-S, which means:

Well-Centered. Original Gum.  Nice wide side selvedge.  Hinge remnants.  Scarce.

Scott Catalog Value for OG: $675

Thank you,

Karl Anderson

Anderson Stamp & Coin

POB 51258, Provo, Utah 84605

APS #130744.  I am a full-time stamp and coin dealer; and a regular advertiser in Linn's Stamp News and Coin World Publications (since 1975).