Not quite 4", but 3 7/8" is long in a title. This is a large shagreen etui which would have had a multi-leaf ivory note pad, 'necessaire', c.1750s, and perhaps a stylus, toward the end use of keeping calendar events, invitations, names of people and addresses. Or, for an engineer, jotting notes or calculations, business - additions and etc.,. A 'necessary' and early precursor of our modern iPhones. The inner notepad is no longer with it. I tried to use it for a business card case but standard American cards are slightly too long. Still, a fine early shagreen case in this condition is quite rare and valuable on its own. Shagreen is the fine belly scale leather from stingray. Very pricey and fashionable in its time (mid-1700s), not many survive this well.
Very good to excellent condition throughout, for age and type. The high original and unfaded coloration is superb. There are no missing parts of the old shagreen, which is often the case. A delicate tiny scale (stingray belly) isn't that good at lasting 250 years and yet here this one is, stunning! The pushbutton opener and hinge: working fine. That pushbutton is very likely karat gold, but I didn't test it. Again, these were luxurious goods in their time. A gentleman's gentleman envy item. Full measurements noted on our photos.