EDSAC . computer using mercury registers. Just look at the thing ! I read its an early assembler machine .

https://www.youtube.com/watch?v=Yc945sNB0uA

For a better understanding of the history of assemblers and assembly language, I'd recommend you google the programming language generations a.k.a 1GL, 2GL... etc. You could start with the first generation (1GL) here:
https://en.wikipedia.org/wiki/First-generation_programming_language

The first computers were all programmed using 1GL - direct entry of machine codes by various means - because there was nothing else available. I remember it well.

I wonder how much did it take to program the first assembler with 1GL. Must have been a nightmare.

Its very interesting to trace the computer back to its machine parts. Another "relic" that I have read of is the "Rope Memory" and "Core memory". I presume it can be interpreted as a 1GL program.
Rope memory : Apollo mission
https://www.youtube.com/watch?v=P12r8DKHsak

Magnetic Core memory
https://www.youtube.com/watch?v=X0WnddW5gZI

Patents to Core memory (!) :
https://www.google.com/patents/US3161861

Punchcard IBM.
Just look at it !

Link1: Using the IBM 029 . 1964 : https://www.youtube.com/watch?v=YnnGbcM-H8c

Link2: Brief history of Punchcard machines 1805 - 1980 : https://www.youtube.com/watch?v=YXE6HjN8heg

Electro Mechanical Processors
For the army boat and flight guns, to calibrate the winds and trajectory of the target .

https://www.youtube.com/watch?v=iSKGVncs_ZQ&t=148s

History of Computer Games

Link1 : 1974 - 1979 : https://www.youtube.com/watch?v=dF0vS5ZrMiI
Id like to try Sky Rider from 1978 !

This person is incredible. He goes thru the Powerboard and explains every component. Truely great guy called EEVblog :

https://www.youtube.com/watch?v=clUVEyi_YNM

I am very impressed by this person . Ben Eater . Made his own computer and manually programs it with assembly . wow.
https://www.youtube.com/watch?v=35zLnS3fXeA