The child above was signing at age 4;10.
Watch how this child Juli phonologically acquires the sign WORK as well as how her language develops from one word to a sentence in a time lapse.
This baby began with the "5" handshape, one of a few unmarked handshapes. Then quickly evolved to "A" and finally "S", both also other two of the unmarked handshapes.
This baby's concept of work was probably generic in her observation based on these patterns: dad's wearing a firefighter uniform associated with being gone and then back; mom carrying a black workbag being gone and then back.
At age 3, this child signed left-handed and one-handed, while she was holding a spoon; though she was right-handed. Yet, it was still comprehensible. Perhaps it's an analog to vocally talking while eating. She also demonstrated a sense of humor, joking about her father's different job.