Sign of Profession (?)

In Julius Ceasar, Act I, Scene I, Shakespeare wrote:

FLAVIUS:
Hence! home, you idle creatures get you home:
Is this a holiday? what! know you not,
Being mechanical, you ought not walk
Upon a labouring day without the sign
Of your profession? Speak, what trade art thou?
First Commoner:
Why, sir, a carpenter.
MARULLUS:
Where is thy leather apron and thy rule?
What dost thou with thy best apparel on?

What are the common signs of profession that people carry with them today? First thing that comes to my mind is the civil/mechanical engineer's cap:

Others might think of a carpenter's screwdriver/pencil, a plumber's wrench etc.

                          
Being an engineer myself, I tried to imagine how a computer science engineer might be identified when you see him/her on the streets? Carrying a laptop? Wearing glasses(!!)? I almost started to think that we just do not have a proper sign of profession. But then true light dawned:

If you see him too much on the streets, then probably he is not a computer engineer.

(c) Scott Adams