Hi Chris, I don't think the pattern on your vase above matches the split diamond example shown in Bagley Glass 3rd edition (page142, or page 119 in 2nd edition for anyone who hasn't yet bought the revised 3rd version - if not, why not? It's good!

)
The split diamond pattern is just that: a diamond split down the middle, whereas yours is more complex than that. I agree the
shape of the vase looks like the split diamond vase though.
Perhaps Angela can add more - I'll drop her a line and ask if she can take a looksee for you. :thup: