I think you're mistaken if you got the impression that the museum once had guides. This isn't a recent trend, so far as I know it's been delightfully free from tour guides since 1881.
You had to buy tickets prior to 2001, so that's changed. (Was entry free in its early history too? Not sure.) That used to be your greeting, the ticket desk.
They had an earthquake machine in 1985, it must be the same one.