[sdiy] Identifying phase of transformer primaries

[James Dunn]

I have a large transformer on my desk which I think came out of an old 
Thomas Troubadour organ. I've tried searching for transformer wire 
colour codes to identify the windings, but to no avail.
So far, I have identified 3 windings (9 wires in total - continuity 
tests reveal 3 windings). 2 windings (2 wires to each winding) each have 
a resistance reading of 15 ohms and the other winding has a resistance 
of around 2 ohms between any pair.

I assumed it was a dual primary, multitap secondary transformer and so I 
connected 110VAC to one primary and got +-23VAC and +-13VAC with centre 
tap on the secondary.
The thing is, I'm in the UK and would like to connect the two primaries 
in series but I can't identify the phase of each winding. The colours are:

Primary 1: Red/White
Primary 2: Green/Black

Any ideas?