In short I do not know of an example of an early iron fuzed shell & most of my books don't cover such early ordnance in enough detail for me to provide any leads. It may be worth his while scouring the articles index of the Ordnance Society Journals & Newsletters on the Ordnance Society website in case something on this, or a similar subject, can be found. Certainly a very wide variety of projectiles were used at one time or another & there seems to have been a bewildering varity of carcasses, shells, fire balls, expanding shot and such devises as could be contrived, I am not at all surprised that iron fuzes were used & in such cases they would have had to be well secured if they were not tapered, lest they be driven into the shell by the shock of discharge. Wooden fuzes were by far the more successful. Some notes I made from more modern treatises c1870: Adrian
The advantages of wood over metal time fuzes were initially believed to be chiefly safety, preservation of the composition and causing the shell to act more violently as the fuze hole is more securely closed. However, experience showed that the advantages as to safety and preservation were imaginary and that closing the fuze holes was found of some importance only in the small calibres. Wood was much cheaper and superseded metal time fuzes. Metal of course remained the material for most percussion fuzes and as further technological advances were made, eventually metal replaced wood entirely for fuzes.