Beware of bridge rectifiers

[ppppenguin]

Recently I found some AC128 transistors admittedly 40 years old that were made the opposite way, collector emitter junctions were swapped.

That's a subtle one. Most transistors will work after a fashion with collector and emitter swapped. For small signal applications this normally gives very low gain but also lower than normal saturation voltage. A very few transistors, notably the OC140, are symmetrical. Almost impossible to replace if the circuit needs that special property. The BBC analogue 625>405 converter uses lots of them as symmetrical switches.