Subject: Re: How high will this thing go?
Here is a chart of the historical P/B:
https://www.financecharts.com/...

It shows max P/B was 1.82, average 1.42
You can download the data, but the dates are not regular, sometimes 1 day between rows, sometimes several months.

Interestingly, it shows total 20 yr return of BRK 692% vs. SPY 646%.