This image is the first order placed using the Silver Slipper inlay without address. There were a total of 5 orders placed from 1973 to 1978.

Orders placed for the Silver Slipper, Las Vegas Nevada and showing the address as required by Nevada gaming regulations;
1957, 1961, 1964, 2 in 1965, 1966, 1967, 2 in 1968, 2 in 1969, 1970, 2 in 1971, and 1972.

Now it is possible that the Silver Slipper casino forgot about the required address and submitted to the gaming commission a sample of the chip without address. It is also possible that the Nevada gaming commission upon receiving a sample chip, as required before every casino order goes into production, forgot their own regulations and approved this chip.

Possible?