..and after all that typing, I forgot to answer the quesiton about when Lenovo took over and this isn't a clean answer since integrations and mergers aren't performed overnight.
The T4x series is considered by many and myself as the last of the IBM's, a great majority of the T40's and T41's were made in Japan or Singapore, less of them in Singapore since Singapore labor is more expensieve.
At this time IBM was already using Lenovo of China to make ThinkCentre desktops and more of the components of the T4x's even though other contractors were just assembling more Lenovo Chinese parts into their own assembly process.
This also raised controversy since it was suspected the Chinese could easily insert spy devices into IBM computers which is a large supplier to US Govt Agencies and the unanswered quesiton of whether not the Chinese could infiltrate us through "phantom" chips was a real threat.
IT is certainly possible an embedded motherboard chip could be inserted that could be used to create a real time connection a designtated destination and just monitor for key words, or recieve remote instructions then transmit this data using encrypted methods so even the vicitm would have difficulty detecting it.
IT wouldn't be impossible to detect but theoretically if it occurred and it was discovered Lenovo of China had sold thousands of thousands infiltrated systems to govt agenciess....... it would be grounds for war on our part.
In my opinion the T43 with the larger 15inch screen was the first of the Lenovo's and last of the IBM's since this seemed to be the last model made in farily equal numbers by Lenovo plus older suppliers in Japan.
some in the ThinkPad community feel the newer Lenovos are lesser quality but I disagree and offer that Lenovo's have merits the earlier IBM ThinkPads didn't, such as the newer Lenovos have sturdier keyboards than my earlier IBM models and I had a preferred membership at
http://www.machinaelectronics.com.com since I bought more $6 replacement keys and key springs there any other customer they had I'll bet you.
There the only place I've found that sells individual keys and undersprings and they've never been out of stock now matter what I needed to buy.
$6 per key is alot cheaper than a whole new keyboard.
But the new and incompatible Lenovo Power Supply was baffling since IBM used the same power supply connector for more than 10 years and they're interchangeable, this is important if you travel for a living and you're at a client site and your power supply dies.
Chances are they use ThinkPads and their IT group can loan you a power supply until you find a store in town that sells ThinkPad powersupplies and other parts.
Try finding a Dell power supply in a retail store.... not likely.
Regardless of whether or not you think Lenovo beats IBM Japan, they all still have that annoying driver model where you have to download 1/2 GB of drivers files and the useless executables and config apps when all you really wanted for four *.sys files and a couple of *.infs !!!!!
That´s pretty nice "little" collection you have there 