Chicken wire mesh on Sherman Firefly turret.....

[David Herbert]

It is also most unlikely that you will find any hint on fixings from inspecting real Shermans. Post war it was pretty much universal to remove any non standard additions from serving vehicles when they were overhauled and any weld marks would be ground off flat. The only possibility would be tanks that had been knocked out and then preserved but even those tend to have been tidied up in the name of safety or 'preservation'.
As Jakko said, your best bet is to find a close-up photo - possibly of the crew in the turret showing the top half of the turret?
David