Closing rim on sandcast gauges

[CB750faces.com (Lecram)]

I have here a sandcast gauge and it seems that the cover has been opened and closed. The rim at the bottom of the base plate isn't as smooth as the rim on the NOS K0 diecast gauge I have.
Does the rim on the sandcast gauge belong smooth as well?

Left: the diecast and at right side the sandcast

[kp]

Looks to have been coated with something or some sort of process has been employed

[CB750faces.com (Lecram)]

Looks to have been coated with something or some sort of process has been employed

Thanks Kerry,

So also the sandcast gauges are being closed as the left gauge on the picture?

Marcel