How can I view which machines are acting as browse masters?

A. There are 2 utilities shipped with the NT resource kit (one GUI, on command line) which can be used to view current browse master status.

BROWMON.EXE - Select from the Diagnostics Resource Kit menu. The master browser will then be displayed for each domain. Double clicking on a machine will then list the other machines that are browsers and a subsequent double click on these machines will tell their status, e.g. backup browser.

BROWSTAT.EXE - Start a command session. There are a number of commands that can be used, however to get a general view enter the command
browstat status
Browsing is active on domain.
Master browser name is: PDC
Master browser is running build 1381
2 backup servers retrieved from master PDC
\PDC
\WORKSTATION

As can be seen the master browser name is shown, as are backup servers.