Actor's Library?

[The Well]

Im an ignorant in this field, so asking a basic question (but a minor one within:

In the OUATITW scene, when two Frank's guys Logan and Jim are to take of the woman, when they see that also Harmonica is involved, one of them takes a look of a hesitation at his companion before they go on. This same kind of look was presented in For a Few Dollars More, when the two guys prepared to protect their vilage stared at Clint shooting the apples off the tree and one of them expressed his hesitation to face Clint in the same "actor's look/glance" as in the OUATITW.

I do not think that that look/glance is a Sergios's special, I believe its a standard actor's expression taken from his library and all that needed to be done at the shooting place was to call out "hey, librery item X!".

Anayway, however that look may appear simple, Im not sure I could repeat it. The same holds for Maurin McBain's role.