Hehe ~ ~ ~ Just show your sincerity.
In fact, the probability of receiving a reply from Allen's letter is relatively high, but it is generally a letter from a brokerage company, and its content is also very formulaic and meaningless.
So if there is no signature photo, it is basically equivalent to giving it away for nothing.
As for the time, it is usually one to two months. If it exceeds two months, there may be no hope.
Finally, good luck!