134mm rear dropout spacing on Al frame My bike has an aluminium frame and I measured 134mm rear dropout spacing. The wheel it came with has 130mm OLD. The dropouts are quite a bit flexible, the QR pulls them in on tightening.
This is the wheel it came with as far as I remember. I am the first owner, but rear and front rims while looking very similar don't quite match. Cannot remember to have (had it) changed.

I am driving this bike for years and thousands of kilometers without breaking the dropout. After a recent need to replace the sprockets and discovering that even the 12-34 megarange freewheel is not available any more I decided to upgrade to freehubs and cassettes. Got a used 7-speed hyperglide wheel to match the measured 130mm OLD of my old wheel and transplanted a current 8/9 freehub onto it, staying at 130mm OLD.
Conversion is done for some time and drive quite a bit with it, but there remains a nagging thought:

134mm is a weird spacing, isn't it? I checked with bolts, the dropouts are parallel, unclamped, and they still look parallel clamped to 130mm.

Could this be a 135mm frame, set to less dropout spacing by long use of a 130mm OLD wheel?
And is 130mm OLD the way to go, here?

Before transplanting I tried putting in wider hub: pulling the dropouts slightly apart I was able to get it in.
The 130mm hub is easier to get in and out and I have been using such for years and miles.
On the other hand, 135mm is "closer" to 134mm and would allow for less dishing.
Your frame is most likely intended for 135mm spacing and measures 134mm either because of manufacturing tolerance or because it was bent by using too narrow hub. The angle difference between 130mm and 135mm hubs is about 0.4 degrees, which is not really visible to naked eye.

135mm would be the way to go, but there is no immediate danger from keeping using 130mm either.