This is an original vintage Frost Cutlery box from the Imai factory in Seki, Japan, made circa 1980s. The interior dimensions are: 1.25" wide x 5.25" long x 0.75" tall. It is marked with model number "F-375" on one end and also "139-51" on the other end (sticker put on by factory). Empty box only, no knife. Seizo Imai was one of Seki, Japan's finest craftsmen and most famous knifemakers of the modern era. Imai made knives for Parker, Frost, Browning, Explorer, Compass, Condor, and many others, including his own brands Imax and Seizo Imai. His custom Loveless style knives are works of art.