I don't think these were the particular gardners transformers used in early Neve consoles, because the modules I have seen with them they used gardeners for the mic inputs & a 600:600 is not the right ratio. The line i/p & o/p were still Marinair if my memory serves me right.
The 7544 was one of the possible recommended o/p transformers for balancing Audio & Design units (who made the helios compressors). It was either that or the 7524. The input transformer they recommended was the 7530 which is 10k:10k. See attached pic.