It seems that your friend is a Samaritan, who have the custom to give their babies a sculpture in the likeness of a pigeon when they have a berit milah.
We learn in Chullin 6a:
כי הא דר"ש בן אלעזר שדריה ר"מ לאתויי חמרא מבי כותאי אשכחיה ההוא סבא א"ל ושמת סכין בלועך אם בעל נפש אתה הלך ר"ש בן אלעזר וספר דברים לפני ר"מ וגזר עליהן מאי טעמא אמר רב נחמן בר יצחק דמות יונה מצאו להן
Like that case involving Rabbi Shimon ben Elazar, in which Rabbi Meir dispatched him to bring wine from the area of the Samaritans. A certain elder found him and said to him: “And put a knife to your throat, if you are a man given to appetite”, (as a warning to distance himself from them and not to drink their wine, because they were not reliable). Rabbi Shimon ben Elazar went and related those matters before Rabbi Meir, and Rabbi Meir issued a decree against them. What is the reason that the Samaritans are deemed unreliable? Rav Naḥman bar Yitzḥak said: They found that they possessed a likeness of a pigeon.
So, the elderly man in the Gemara warns us that every Samaritan owns the likeness of a pigeon.
Tosafot ad loc. explain that:
דכל מקום שהוא מזכיר ההוא סבא הוא אליהו
Whenever the Gemara mentions 'a certain elder', he is Eliyahu.
How did Eliyahu know that the Samaritans have these pigeons?
Well, we know that Eliyahu appears at every berit milah. So it must be that the Samaritan custom is to make the pigeon and give it to the child in honor of his berit, which is how Eliyahu became aware of it.
Although a berit milah normally takes place on the eighth day of the child's life, your friend's grandson must have been seriously unwell, and only recovered when he was 23 days old. They would therefore need to wait one week, until they are able to perform the circumcision, and give him his pigeon, when he is 30 days old.
Finally, I'm guessing that your friend is so excited about the birth of his grandson that he wants to make the pigeon out of silver, which is why he wants your silver tray. I would be wary of giving it to him though, bearing in mind the second commandment.