NavList:

Have you looked into Chip Scale Atomic Clocks?  Somebody mentioned $1500 but I don't know for sure.  Don't know what the power requirements would be either.

Re: Timekeeping in the post-WWV/post-HF world
From: Steve Dunlop
Date: 2018 Sep 25, 08:48 -0700

....

I'm looking for a self-contained time reference to use in the event of a loss of GPS.  I am presuming a boat that is not equipped with HF gear, because of the obsolescence of the shore stations on which it depends.

My real question is: what is reasonable, and is the standard answer of three Timexes really the best we can do?

I get it on the constant error rate.  I'm not sure that the error rate of the average cheap digital watch is as constant as is widely believed particularly when the watches are not stored at a constant temperature.  That approach requires regular checks.  Maybe having a ship's clock and a HAQ watch that are both accurate enough to use without rating would be a better answer given that they are available, compact, and low cost.  I'm thinkout out loud, I guess.