Not grain, thats another dubious weight unit nobody knows. Except people who make their own ammunition perhaps. I'm talking about gram, the metric weight unit that the entire world uses, except the US, Myanmar and Liberia.
And of course it matters what the weight (gold/silver content) of a coin is. Only that matters, actually, nothing else. Just wait what happens after the dollar falls off a cliff, and everybody loses all his savings, pension funds and all that. If then someone only whispers the word dollar, people will hang him in the next tree. And they will have no trust in anything that is not tangible, at least for quite some time.
Have you seen this?
https://www.usdebtclock.org/
Nearly 32 trillion dollar debt, thats 32,000 billion. Or nearly 100,000$ for each and every citizen, from the new born to the oldest pensioner. And the number is growing by the minute. Have you got 100k ? So where has the money gone?
Thats why I dont believe in the future of a fiat dollar. Even if they would make a 100:1 reset, as you forecast, the real value of the new dollar would only be 0.1 cent or so. Thats how bad it really is.