Port glass removal?

<table width="100%" border="0" cellpadding="0" cellspacing="0"><tbody><tr><td class="Forum_PostBody_Alt" valign="top" width="80%" align="left" height="100%"><table width="100%" align="left" border="0" cellpadding="0" cellspacing="0"><tbody><tr><td valign="top" width="100%" align="left">I've got the old bronze ports without any visible means of connection between the inside and outside frame. I need to replace the glass and can't figure out how to remove the outer frame, anyone?
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BS2 has the right idea ,

BUT be aware you will possibly need to create a tool to reinstall the ring.

The hassle is most of the rings are not flat , on purpose , to tension the glass when installed.

WE have 12 inchers on our 90/90 and it was a bear to remove a cracked glass and then install a lexan flange to hold the high speed spinning window , for winter operation.

On mine the inside ring is the frame and the outside ring is the removable piece but there aren't any screws or fasteners visible. It looks like the ring is pressed in place into some sort of setting compound that also seals the glass.