You also need to check a different light level as non linearity can be a problem, cell, battery, meter
Levels brighter and darker than you normally use.
Then you need a silver shot to confirm.
With LF Id build the shutter speed tester and confirm actual shutter times allowing for efficiency.
On a cold soak day the shutter is the biggest 'variable' in your error budget.
I use Westons and do a similar check Weston to Weston.