Theory:

     Then the older man seemed to feel a little easier, took out his hand from his pocket and quickly looked at the watch on his wrist. “How much will you give me for this?” the man wrote.
 
     Ray noticed a little shame in the grey eyes looking at him. The watch was nothing special and yet had great powers. It was something to exchange, a way out of a bad situation. Knowing that great need had brought the man to his shop in the first place, Ray asked, “How much do you need for it?” The reply came back on the notepad: “Whatever it’s worth.”
Explanation:
 
Looking at the loan board, the man started to feel a little easier and relieved.
 
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The man looked relieved
 
He must have realised that he had an option after all. He released his hand from his pocket and quickly looked at his wrist where his watch lied.
 
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The man released his hand from his pocket to look at his wrist watch

The movement of the man’s hand and eyes are symbolical. The hand leaving the pockets and his eye darting at the watch suggest his attitude and intentions. When the man released his hands from the gun, it indicated that the man was no longer thinking about using the weapon. The act of looking at the watch, on the other hand, implies that he has realised that he has an option to get money in the right way and that there was a scope for hope.

The man then wrote on the notepad for the first time. He wanted to know how much could he get for the watch. He wrote: "How much will you give me for this?”  The man looked a bit ashamed when he wrote the question. He knew that the watch wasn't that great or worthy. Ray seemed to have recognised the shame in the man's grey eyes.

Ray knew that the watch was nothing special, but it held great powers at the moment. The watch could act as a bridge between wrong and right. With that watch, the man could pledge it and get money. He won't have to commit the crime that he had intended to do. The watch was indeed something to exchange, and it was a way out of a bad situation.
 
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The watch was nothing special and yet had great powers

Realising that the man might have had great and desperate need for money, Ray asked the man how much he needed. The man responded on the notepad by writing, "whatever it is worth".

Interestingly, the line "how much do you need for it?” was conveyed by Ray through speech rather than writing. It was the first time that Ray was seen talking. The line confirms the fact that Ray is not mute. However, it also raises another question: why did Ray decide to speak now and not earlier? This question yields to a fascinating study of psychology.
 
You could say that Ray had used the technique of communicating through writing to buy himself more time. Writing gives Ray and the man enough time to think over their thoughts. Ray must have realised that he should act calmly and slowly if he had to convince the man. Moreover, if Ray had started the conversation by talking, the man wouldn’t have considered or accepted the written communication as an option. Hence, they wouldn’t have communicated, and things would have turned bad. Finally, Ray decided to resort to speech because he probably realised that the man was no longer dangerous.
Reference:
National Council of Educational Research and Training (2006). The Old-Clock Shop (pp. 11-14). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.