first time ever.

the bob jackson site has great info on reynolds. anecdotal yet technical.

since you seem better-versed on this than most of us here, what do you think accounts for someone using both 4130 and 520 in the same frame? are they different enough to make one better for, say, main triangle use and one better for stays? or, is it more so they can keep the costs down and still put the 520 sticker on the frame? i came across a few forum posts in a search where someone was saying to be careful because you sometimes will see 520 stickers on frames with 520 only being used for the seat tube.

thanks, cheers.

yeah cost. and the sticker.

4130 is pretty generic stuff. it's composition can vary within a certain range. and standards say that it is "weaker" than 525.
I'd assume that Reynolds might have slightly tighter tolerances on their composition.

and yeah, as long as 1 tube is 520 then they can put the 520 sticker on.
This is actually quite common, even dating back to the 531 days.
Reynolds made a whole series of 531 tubing decals to indicate which frame tubes were actually 531 and not hi-ten. There were also 531 decals to indicate SG vs. butted 531.

here's some info:

https://www.worldclasscycles.com/JACKSON-HOME.htm

the type of sticker like a square 531 sticker, or a triangle or a rectangle with 531 on an angle across it are all for the differing builds: tt and dt, main triangle, whole bike, just stays... not necessarily in that order...