This is extremely well conserved Muromachi era Ko-Tosho Tsuba. Motif is butterfly which might be the symbol of peace. This tsuba is much better condition appeared in Sasano's book and much bigger. This has the size of 85.6mm width, 85.8mm height, rim thickness 2.6mm, and seppadai thickness 3mm. Probably made in Mid-Muromachi, Eisho era which is about 500 years ago!