I assume with your statement that you have had many years working in the advertising business and with trade shows as I have. Putting out ads with a restriction on how people can attend an event to spend their money is a failing strategy. Success results from inclusion not exclusion. Statistics show that opening a show for three days to the public has shown better results than one open for two days.
How much of your business was promoting public events?
Is the York meet a trade show?
I do have experience in this area.
As Marty wrote: "Whats so hard about advertising a 2 day train show. If you don't advertise a third members only day then nobody knows. It's not rocket science. Advertise the open days. Period."