Most need the rear cover to be removed.
I'm sure there are at least a few boxes with access holes in the rear cover.
The only one I can think of off the top of my head is the Realistic SCR-8.
Some boxes need further disassembly than just the rear cover to access it so you're lucky.
Here's an older thread of mine where I drilled access holes in the battery compartments of two of the same boxes I refurbished so they can be adjusted without any disassembly in the future.