Auto data says 950grms R134a, 140-150cc oil pt. no. A0019890803. sounds about right to me.
I take it you have access to charging kit etc. I have too, handy!!
I have a 96 E280, air con worked but not very well in traffic and the low speed fans weren't cutting in as they should with the air con on. Bought a cheap recharge can from Halfords for £20. Kept topping it up till the low speed fans kicked in as they work on 12bar pressure. The system only needs 2.6bar for the air con to work but it doesn't work very well. 25bar is about the max you want on the high pressure side when warm. Don't know if this helps at all.