Visual chain identification I have a second hand bike and the chain doesn't seem to work well with the 11 speed cassette fitted.
It almost seems too wide to fit in the sprocket gap. Are there any visual signs on a shimano chain which indicate whether it is 10s or 11s?
With accurate vernier calipers or a micrometer, measure the width of the outside plates.
https://en.wikipedia.org/wiki/Bicycle_chain#Width shows this table of chain widths.




Speeds
Width




6
7.3 mm (9⁄32 in) (Shimano HG), 7.1 mm (9⁄32 in) (SRAM, Shimano IG)


7
7.3 mm (9⁄32 in) (Shimano HG), 7.1 mm (9⁄32 in) (SRAM, Shimano IG)


8
7.3 mm (9⁄32 in) (Shimano HG), 7.1 mm (9⁄32 in) (SRAM, Shimano IG)


9
6.5 to 7.0 mm (1⁄4 to 9⁄32 in) (all brands)


10
6.0 to 7.0 mm (1⁄4 to 9⁄32 in) (Shimano, Campagnolo)


10 (Narrow)
5.88 mm (7⁄32 in) (Campagnolo, KMC)


10 (Narrow, Direction)
5.88 mm (7⁄32 in) (Shimano CN-5700, CN-6700, CN-7900)


11
5.5 to 5.62 mm (7⁄32 to 7⁄32 in) (Campagnolo, KMC, Shimano CN-9000)


12
5.3 mm (13⁄64 in) (SRAM)




So if your chain is 5.8mm wide then its probably 10 speed, and 5.6mm is likely 11 speed.   The difference is small, 0.2mm is about 8 thousandths of an inch, you're not going to see that on a ruler.
However if you had known 10 or 11 speed chain laying flat on a tabletop, and your current chain flat beside that, you should see a visual difference, or at least feel one with your fingers.

Another idea is to look for a quicklink or master link.  Many of them have 10s or 11s stamped into the sides.  You're unlikely to get an 11s master link to close on a 10s chain, but the opposite is certainly possible.