The tx0 series are based on an ARM CPU. I'm not too sure when the Tx0 was launched but the model publicity data pdfs were created back in May 2011. At that point there was the T10 (zero client, no flash) and the T50 (1GB Flash). Subsequently the tx0D came along with a dual core CPU. I haven't been able to locate a launch date for the 'D' model however it was in existence in 2015/2016 when Dell decided to rename various products they had inherited from Wyse.
Broadly speaking the Tx0 range became the 3010 and the tx0D (aka 3002 and 3012) became the 3020.
Being ARM based I have not done anything with the Tx0s but there are others who have and the details are on the links page
This entry draws heavily on the models datasheets.
The Tx0 / T10
The T50
The Tx0D