Distribution

Technology does not advance evenly.

For example: Afghanistan lacks almost all of the infrastructure we take for granted in the US and their manufacturing base is, maybe, GURPS TL4.  TL5 tops.

Yet TL8 electronics abound.

This made me rethink a lot of things in a Traveller campaign.  The TL3 non-industrial agricultural world with a feudal government is going to have state of the art consumer goods because some free-trader is going stop off and trade a load of the stuff in exchange for whatever the they can get.

Free traders are experts at arbitrage.

A non-industrial agricultural world might (almost certainly) have the wealth to purchase modern farming equipment even if they cannot be manufactured or serviced with local know-how.  The Imperial equivalent to Allis-Chalmers will also send teams of people to do that service post-sale for a fee.  It might even be appealing to these people to live in a pastoral, low pressure, low-tech environment between jobs.  They won't really be giving up much in comforts, consumer stuff is widely available!

Compact, self-contained, fusion generators are going to be prime trade-goods.

I don't think there's a good real-world model for the kind of trade that operates on the fringes and free-traders serve.

It also hits me that someone from that TL3 world, as a citizen of the Imperium, has the right to enlist in the Imperial military.  That heavily implies that the Imperial military has a remedial program that brings these volunteers up to speed on modern technology.