GPZ1100A Unitrack dash glass removal.. Anyone know how ???

As title.
Does anyone know how to remove the glass from these Unitrack clocks.
There's a rubber seal and a plastic ring holding it in which i presume is probably is a snap fit and not meant to be removable.
I want to remove the tacho glass without buggering up the plastic ring etc and fit a boost gauge in there.
The Drouin Supercharged Zed is getting a makeover 

Wish i had more info to share 1015 but i've never had any experience with these. But does seem the shared big black shared cover is thermo-welded to the gauge mechanism/illumination white flat plate. There is, seem a variation of the same, GPZ750. Eventhough a 150MPH speedo, comes apart. It comes apart because the speedo is offered separately. Part number 25005-1218. Here are a couple photos i found on ebay of someone's attempt of    removal, ain't pretty ha.  

I have several sets of 750 and 1100 uni clocks and they are pretty much the same except for the dial increments etc.
The black top and bottom covers simply lift off once two screws are removed.
Non are bonded to the white core as stock.
It's how the glass is secured which is currently a puzzle.
The glass has a rubber sealing ring either side to keep it weather tight ( which is likely a one piece grommet affair which surrounds the glass edge )  and a 7mm-ish deep plastic ring on the underside that seemingly holds it all in place.
I though it may be a snap fit in the case but i can get a feeler gauge down the side of the plastic ring between the main body all the way round to the same depth as to where the rubber is which is strange.
I've had it in hot soapy water to see if it will just push out but no joy and there's no movement of the ring.

 

I wonder if the ring sits in a groove? Does your four jaw chuck open wide enough to “stretch the outer case ?

Ah well !
The problem solved itself.
The bloody glass cracked and the ring remains solid .
Luckily the gauge is a perfect push fit in the ring so that's how it will have to be.
Not keen on the chrome bezel which i was hoping to hide by fitting the gauge in from underneath but it will have to do for now and i'll see if it grows on me..




 

Looking at your pictures that ring looks like it’s bonded in !!

If the chrome does not work for you, you could paint it.

You got lucky with such a nice fit!! The lens was glass? You can have those made of course if you're wanting to go that direction. The only plastic shroud gauges i've ever done were on the first year Suzuki GT750. The ones with the black plastic upper and bonded-in acrylic lens. I think it might grow on You, it's a performance thingy! Great Job!