Thank you for showing this rarity, Chris, and thank you, Paul, for showing the corresponding Sowerby design representation.
I was drafting out this reply before Paul had posted his reply, so there may still be some crossover of information.
Sowerby pattern 1505 is shown on page 10 of their pattern book IX (1882) , but I can't recall seeing any photos of actual examples anywhere else. The design representation describes it as a 'vase' as do Simon Cottle and Jenny Thompson.
The lozenge is for 24 May 1880 - Parcel 8, which covers a bundle of 11 designs - RDs 350083 to 350093 inclusive.
Simon Cottle ("Sowerby -Gateshead Glass", page 103) collates most of the RDs in the bundle with their pattern numbers as follows:
RD 350083 pattern 1480 bowl IX, p10
RD 350084 pattern 1482 sugar basin IX, p10
RD 350085 vase
RD 350086 dish
RD 350087 pattern 1473 basket IX, p9
RD 350088 pattern 1475 basket IX, p9
RD 350089 pattern 1482 bowl & jug IX, p10
RD 350090 pattern 1477 bowl IX, p9
RD 350091 pattern 1474 trinket IX, p9
RD 350092 pattern 1476 trinket IX, p9
RD 350093 butter dish
Now, thanks to Paul, we know that RD 350085 is definitely Sowerby pattern 1505, and, assuming that Cottle's collation of the other RDs is correct, that only leaves RDs 350086 and 350093 from the bundle to be allocated their corresponding Sowerby pattern numbers.
Fred.