Your Dad is quite correct, Mike - Sowerby pattern 1563 it is. Well found.
I have re-checked Vol.3 of the Thistlewood Sowerby CD-ROM catalogue and the pattern 1563 covered butter is shown on page 6 of the 'Sowerby Glass in Pictures' thumbnails and as a photo example in the linked pic.
Page 7 of Pattern book XI (1885) also illustrates the butter in the far left of the bottom row but the pattern number is missing from that particular page in the Thistlewood CD-ROM.
Hashinbaby, may I have your permission to add copies of your photos to the Sowerby Pattern Numbers section of the GMB Glass Queries Gallery for permanent reference, please.
Fred.