Can you help to identify these frames, bikes or parts?

cast or stamped fork ends/dropouts?

Stupid question, how to I tell the difference?

I think the Sun Solo is just a generic gaspipe frame.
Best ways to quickly check are...
1) pick it up - does it way a lot or not a lot....
2) Measure seatpost size 27.0 or 27.2 - might be 531... 25.4-26.8 probably gas pipe

Weighs a bit, but not as much as I expected for a steel frame that size (53cm ST).

Seatpost is 25.4mm

Either way I'm happy with it as a commuter. Lovely smooth ride, comfortable, and light enough that I can bunny hop it over unexpected potholes.