Don't believe I've ever seen one of those Nick ..... you've sure been hiding lots of way cool stuff!!!
Unfortunately this one will never be fired as they are very common with cracked fireboxes after being fired.
I don't mean to get out of line but mine was fired and has at least twelve cracks in the fire house.
I took it apart and it was packed between it and the boiler with polishing compound. That may have
been the problem with expansion. Didn't know they were numbered, have to check mine.
Oh Nick if you know how to move this up into place please do so. Thanks.