206 & 207 On Cover Philatelic Use?

Whenever I see Nassau Street anywhere on a cover I assume a stamp dealer is involved.
Would there have been any reason to add a 1cent stamp to this cover?

Letter rate is 2 cents per half ounce beginning Oct 1, 1883. This would be a double-rate cover. Sent to a relative. In my opinion, not philatelic even if from a dealer.

The rate before the change was 3c, so the 1c is a way to use the old stamps.

Thanks!! I have much to learn about postal history.

Possibly philatelic and possibly not. Frank was not a stamp dealer, he was a lawyer whose office was on Nassau Street, along with a whole herd (passel? pride? gang? - what's the term for a bunch of lawyers?} of other lawyers who had their offices on Nassau Street. As an attorney he might have also had a hobby of stamp collecting especially since he would have been surrounded by stamp dealers every day on his way to and from his office. If so he might have been similar to other collectors in using interesting and out of date stamps on his mail to his family so he could ask them for the envelopes for his collection. One will never know.

These are in period, not out of date. No reason to think it's philatelic.