Two of the greatest tsuba artists of all time are Nobuiye and Kaneiye. Both did outstanding work in iron tsuba around the end of the 16th century and both are recognized as true masters of metalwork. Even when they were alive their works commanded high prices and were above the means of the average Samurai.
One clever Samurai was able to incorporate the works of both of these masters on his sword by having these deceptively accurate copies of one of the famous works of each of these masters fabricated as iron menuki for his sword. These are outstanding copies that invoke the spirit and workmanship of the originals and they are also just a lot of fun.
They are about the size of a dime as can be seen in the photo above. They were made by an artist of the Umetada school as evidenced by the signature on the reverse. They have been authenticated by the NBTHK and have been awarded Hozon tosogu papers.