Yes it is

St Isaac's history in links below
I have read that the dome was made with 100kg of pure gold!
According to Wiki it is the largest orthodox basilica and the fourth largest cathedral in the world.
It was designed by architect Auguste de Montferrand.
Wiki says 'The cathedral's main dome rises 101.5 metres (333 ft) and is plated with pure gold.'
'The cathedral took 40 years to construct, under Montferrand's direction, from 1818 to 1858'
https://en.wikipedia.org/wiki/Saint_Isaac%27s_Cathedraland beautiful painting of it here
https://en.wikipedia.org/wiki/Saint_Isaac%27s_Cathedral#/media/File:Surikov_horseman.jpgI've been looking for an egg for a while and then this one came along for a snip.
What I have found out so far:
I think it was probably made anytime from 1992 to now.
I have read that they were produced 1992 - 1996 and then production slowed down. I have found a different one though that was marked Christmas 2007. So they are/were still being produced somewhere, although I don't know if that one was solid rather than hollow. So it might be that the the hollow ones ceased production in the 90s.
Most of those I've managed to find are red, green or blue or purple. There are very few clear glass eggs.
They all seem to have different designs - I've found one matching pair together, but hand engraved, in different colours. Otherwise, they all seem to be quite individual. Many (modern) have the Russian Eagle and crown on in some way.
I have only found one other with St Isaac's on it, and it was clear glass, engraved and gilded and the engraving 'cruder' than the engraving on mine.
I have found some with different labels on the bottom, some in Russian some English as well, but perhaps either different makers or different periods.
All those I've found apart from the old ones (very few), that I believe are modern production and are also hollow (mine is hollow), appear to have a ground base unpolished. The base on mine is completely polished clear.
I had not intended to collect souvenir glass but have somehow ended up with one ruby overlay engraved becher, one Russian egg and one triple layer overlay cut, gilded and enamelled becher ... somehow making a collection

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