Most collectors pay little attention to the back sides of old bonds. For the most part, these are simply utilitarian -- a place to record the transfer of bondholders. Bonds were often folded in quarters and so a title panel was frequently included, but nothing fancy.
But there are a few bonds that the issuers decided to dress up, paying an extra price to the banknote printing firm for additional engraving. My suspicion is that these bonds tended to be riskier investments (think junk bonds), so the issuing company did everything they could to make them appear impressive. This was definitely the case with West Shore Railroad.
As I go through my collection now, I've been checking the backs to see what surprises I might find. I'll post the most interesting ones that I come across.
If you imagine the patterns made by an old Spirograph, that is the basis of a geometric lathe. These were first invented to do ornamentation on jewelry, pocket watches and things like Faberge eggs. But someone realized that if you engraved the patterns on to a flat metal plate you could then use it for intaglio printing as well.