In general terms, we learn some rebars have the same appearance so that lots of people can not identify the rebar themselves, which may cause mistake easily. In order to avoid this situation, we show the ways to identify rebars by their markings.
So if you want to learn more knowledge about reinforcing bar or you want to check whether the rebars you bought are right size, you will not regret to be here.
ASTM rebar markings:

Size #11,Grade 60, A 615
A range of individual markings reveal the identification of each individual rebar:
The first letter or symbol means producing mill and deformation pattern.
1.     The second marking means the bar size, in this picture, " 11 " means the diameter of this rebar is #3.
2.     The third letter represents the type of steel as follow:
a. S: Carbon-steel(A615) 
b. W: Low-alloy steel(A706)
c. R: Rail-steel(A996)
d. I: Axle-steel(A996)
e. A: Rail-steel(A996)
3.     The last marking shows the grade of reinforcing bar.
a. 40: grade 40
b. 60: grade 60
c. 75: grade 75
d. 4: grade 420, also grade 60
e. 5: grade 520, also grade 75
Furthermore, the grade also can be identified by its additional lines, which must be at least five deformations long, for example, in this picture, the first rebar has one line only, which means the grade of it is 420. If it has two lines, it represents grade 520, and no line means grade 40.
CSA rebar markings:

Size 20M, Grade 400

Size 20M, Grade 400W
cr. http://www.reinforcing-bar.com/technology/reinforcing-bars-iden