Oh my! Perhaps I have expressed myself in a confusing manner. There are two versions of the "chrome Z", hollow cast and solid cast. 76807-E4600 shows application up to 1-70 and replaced by E4601. E4602 shows application up to 12-70 when it is replaced by E8200 which I believe to be the round vented emblem to coincide with the vents in the quarter wings. Of the early 240Z emblems, they come in chrome Z metal, white Z metal and white Z plastic. I have no idea what part numbers go with these.
The point I was making was VERY anal and just a point of interest. Before there were chrome Zs, metal cast, and hollowed out on the back side, there were chrome Zs, metal cast, and solid. Here is a picture of mine. Solid hunk of metal - quite heavy. This emblem, as I heard from Mr. Matsuo, was the original prototype production emblem. Several hundred of the first HLS30s were fitted with solid cast emblems and every one I have seen came off a 1969 production car- pre December.
Of course, this is very anal. Once you put the emblem on the car, you can't tell the difference. I bought this on eBay many years ago and got into a bidding war with another member on this site whom I did not know at the time. I paid $100 for this.