Merc Atego 815 - is there any clutch wear indicator?

Hi,

My driver reported the cluch on my 2006 Merc Atego 815 stayed pressed in a few times, but it was OK to drive back once he pumped it up. My garage said it’s either the master cylinder that’s failing or the cluch is near the end of its life.
Please can somebody tell me if it’s possible to check if the cluch is worn out withouth removing it from the vehicle? A mechanic friend (who is very good, but lives too far away) tells me there is either a window you can see through or you can judge by some pins, but the garage insists on taking the gearbox out to check it. This would mean putting a new cluch kit on as the old one “will likely be worn out and it won’t be worth putting the old clutch back in”. I agree with the amount of labour involved it makes sense to put a new clutch in, but is there a way to gauge it without taking the gearbox out?

I’m afraid of using this truck before it’s fixed as I don’t want it to fail on the road so it’s parked up today and driver on a day off.

Many thanks

The matter is now sorted.

This Mercedes master cylinder problem, (pedal on floor) goes back to the time of the NG Mercs!