How to open up (old) Bosch drill? Any tips?

[Lusi83]

This is a Bosch drill CSB 550RE - I'm guessing about 30yrs old ....
Has stopped working and I suspect it needs new carbon brushes. Has never been taken apart since I got it new.
I have undone the screws (8) but I can't get the case to come apart. Looked online for repair videos to see what I'm missing but I can't find anything -no hidden screws etc.. One is speeded up and it seems to almost fall apart, another couple it does seem more difficult, but both just insert a screw driver/blade in different parts of the case and it comes apart. I've tried these areas, I broke a plastic blade trying to do this, I've tried with a screw driver, a blunt (butter type) knife - I'm damaging the case now - I am working around the case and and have managed to get areas loose, but there is one area that is still tightly closed and won't budge. Looking at the videos I can't see any obvious clips or anything to target
Does anyone know if there is a knack to this? Had similar experience?
(This was the first powertool I got, it was a present and even though I have a cordless drill and an sds drill this is still my go to for lots of things -would love to get it working but worried the case is going to be too damaged at this rate)
Thanks

 

[CountryFan]

https://www.toolspareparts.com.au/media/catalog/product/cache/7bc98fe5a14b2cf376a5dfc7585847e8/8/3/83855.png

Any good?

 

[big-all]

mind and cut the label down the joint in front off the trigger

 

[Lusi83]

I have looked at the exploded diagram (and have looked at other ones too) and I really can't see anything on there that would explain why it is so difficult.
The label - the case splits round the label (it a kind of dog leg) so you don't need to cut it.
There aren't any screws shown on the diagrams under the labels on the sides and I can't feel anything under. (Also like I said I have looked at a few videos of people working on this drill and I have underdone all the screws they do)
I've manage to get it open (loosened) everywhere but on the top near the trigger that changes from hammer to standard.
I've always looked after it - I actually bought the SDS drill as I was trying to dig out some stubborn brickwork and I thought it was too much for it...
I am trying not to lose my patience with it -so keep leaving it for a while...
(also its a bit upsetting - it was a present from my dad who died a couple of years ago and it is the kind of thing that I would have taken to him to look at, especially as he had one just like it)

 

[big-all]

just checking the second handle is not fitted behind the chuck??

if its holding around the top surface fully close the case and start at the top edge incase its locking the top together by opening bottom first
tend to work best iff both sides move parallel away from each other as in ease apart 2-5mm all round increasing in small steps all round

if you have a rubber mallet or normal hammer with a rubber handle try drumming around over the joint impact on both sides equally at the same time avoiding contact near switches but go all the way round