Legal notice without advocate's registration number

What the first step should be taken if one receive a legal notice without advocate's Stamp and/or Registration number?

Legal notice sent by a advocate need not be mention his registration/enrollment number with the Bar Council of the State where he practice as an advocate. Similarly, an advocate doesn't require a rubber stamp to be affixed on the notice sent by him, it's good if the notice has his name and addresses etc. mentioned.

well expalined.Thanks.