Help please. Can’t remove unusual double glazing bead.

[Loz090912]

We are trying to replace window units. The bay is different from others and we can’t remove the beading. Have tried palette knife, chisel. Hammering all is failing to budge it.
Never seen beading like this before.
Can anyone help please. As you can see if we carry on we’re going to damage it.
Thankyou

 

[footprints]

I think you may have external beads. With them you pull out the rubber on the inside then push the glass back and remove the outside beads.

 

[foxhole]

If the black seal is separate it will need removing first.

 

[crank39]

If I could see some pictures I'd be able to tell you