This is not particularly new, as it was discussed several months ago in the thread linked below. I agree it was not a mailpiece but an insert of some kind attached to either a bunch of flyers or a newspaper. The "trick" is to get the recipient to "think" it looks like a legitimate piece of mail in the hope that they will be more apt to open it and not just throw it away.
Interestingly if you compare the bar code below the eagle on your piece as compared to the one at the link below, it is identical, so that alone is a clue that it did not legitimately flow through the mail:
https://goscf.com/t/37403For what it's worth, I did look up the address on your posted envelope and come up with a number of variants in the prescription drug and healthcare fields, so my guess is that the "#xxxx" is merely an identifier so that the telemarketers or mail clerks can identify the source of the ad being responded to.
Just take a look at all of these similar names and addresses:
National Prescription Price Protection, 217 Centre Street, #2830, New York, NY 10013
Healthcare Alliance, 217 Centre Street, #2190, New York, NY 10013
National Prescription Assistance Service, 217 Centre Street, #2450, New York, NY 10013
Prescription Safety Net, 217 Centre Street, #2540, New York, NY 10013
American Prescription Discounts, 217 Centre Street, #2740, New York, NY 10013
American Rx Advantage, 217 Centre Street, #2780, New York, NY 10013
Associated Wellness Network, 217 Centre Street, #4150, New York, NY 10013
Uni Script, 217 Centre Street, #2210, New York, NY 10013
Internet Drug Coupons, 217 Centre Street, #3240, New York, NY 10013
American Prescription Savings Alliance, 217 Centre Street #2280, New York, NY 10013