No Cap or 'Secret Cap', I laughed a lot.
The NXT monetary system has allowed token issuers to back their tokens with a reserve of NXT since 2015.
https://nxtwiki.org/wiki/Monetary_SystemReservable If Reservable is checked, two extra fields appear:
UNITS TO RESERVE: This is the total amount of the currency to reserve, the reserve supply...
MINIMUM AMOUNT OF NXT PER WHOLE UNIT NEEDED TO ACTIVATE CURRENCY: Assuming the ....
Claimable: Claimable currencies are reservable currencies that allow the locked NXT reserves that back them to be claimed, meaning that a current holder of a claimable currency can exchange it for the locked NXT that backs it, in doing so reducing the Current Supply shown on the All Currencies Screen.
New tokens backed by the more larger and liquid NXT token did not appear to provide any greater liquidity or achieve much traction in the marketplace as evidenced by their lack of popularity today. So I can't see an ETH/other reserve token being much different. (The tokens were simply worth whatever the market valued the token at anyway + the amount of reserve currency the token was redeemable for or backed by with no/low liquidity/volume advantage.)
I will read up on the CRR mechanism and how it plans it to do the job better.
The interesting part for me is the ability to diversify one token as multiple tokens. ETFs for coins.