Mine was an A2 like this
I got it in 1959 and it disappeared along with a load of scrap metal from the cellar of my late in-laws house about 15 years ago. I still have the engine from the set, but I won't risk posting a locomotive picture.
The transformer spent more time being abused with my electrolysis and electroplating experiments in later years.
I too drilled out the rivets, it was to replace the mains lead, but it was long enough ago for 4BA to be far more likely to be at hand than M3/M4.