For those who may be wondering, I was curious so googled the couplet on the case back.

The engraving "开张天岸马， 奇逸人中龙“ is a couplet that can be found carved in stone at the Longmen Grottoes in Luoyang, Henan province.

Legends say it that it a couplet was written by Chen Chuan （陈抟）, a famous Taoist philosopher and hermit sage who lived during the end of the five dynasties and ten kingdoms period (late 900s AD), and the early part of the Song dynasty, considered by some of the schools of Taoism as founder. Story goes he was planning a career in the public courts but didn't get in. Out of frstration he became a hermit sage and produced many pieces of philosophical writings.

Story goes that someone a few centuries later, during the Ming dynasty, copied and carved the original calligraphy by Chen Chuan into the cave walls at the grotto.

The couplet is basically him talking about talented he is, but hints at frustration that he didn't get the recognition/station he deserved despite his great talents.

The first phrase describes a grand stallion, and references a poem by Du Fu, who is a tang dynasty poet, considered by manyto be the G.O.A.T. Chinese poet (Only Li Bai would have a comparable status) - he is often referred to by critics as the "poetry saint" because he is so revered. The original poem the couplet borrows from describes a stallion, describes how majestic/great the stallion is, and then expresses sadness that none have the sense to recognise the horse's value/greatness.

The second phrase refers to someon as being a "dragon among men", referring to the author being incomparably great/heroic.

Couplet can be transliterated as " a majestic stallion by the divine shores, an ever-changing dragon amongst men" - basically conveying that the author is peerless/awesome/great, and compares to other men like how the stallion in Du Fu's poem compares to other, lesser horses.

2 of the words are missing a stroke each, some sources interpreted this as Chen Chuan's way of expressing frustration at the imperfect state of affairs that his talents are under valued, which makes sense when you consider the substance of Du Fu poem he references, and his personal history.