If you feel like there is some market for these late 70's quarters, take the next step. Use the quarters you have, have them 3D scanned. The deliverable is an electronic model and potentially a CAD file that would be needed to build tooling to manufacture these. After the part is scanned, sell or use the quarters. The electronic file takes up no more room than a USB stick. No idea what it costs to do a scan of that size, but these days you can likely find someone that can do that in any major city.