Guess I don't get why you think GCOR would only be recent. The GENRAL CODE OPERATING RULES have been around for years and they give specific ways to give hand signals. This is what I meant by should be used.
All railroads has a GCOR test and they have other test that the railroad implies and must be understood specific to their needs, which could be different then other railroads.
As for what era the Boone and Scenic depicts? Well when the steam locomotive was built in 1988 I guess 1990 isn't to far off
Dan