Picking up this old thread, I've recently started (many years late!) on my own SF. Mine was missing it's original toolbox, but I found an item at an a/jumble that at least resembled what I needed. Now that I've come to look more closely, it does indeed seem to match all the pics I've seen of SF T/boxes and also matches the size details provided by BikerJD. But the mounting holes are not for an SF and so it must have come off a different model. Looking thro'' pics of various BSA models I spotted the plunger-framed B32 and also the B34 Gold Star. These used a smaller toolbox than the 'cooking B31/B33 and looks to be the item that I have. It would have made perfect sense for BSA to use up any boxes or tooling made for the earlier B32. Anyway, this is what I'll fit as at least it looks the part! So, anyone searching for an SF T/box - try looking for one from a B32 also - much more common in the UK