This is an old AZO Real Photo Post Card dating from sometime between 1904 to 1918. It was addressed to Mr. Fred Jackson in Centerville Delaware and has a short message on the reverse. This card was not stamped or postmarked, but probably enclosed in a letter, judging from the message.
I wonder if this could be the old Kent County Jail... the one used before the Morris Correctional Institute in Dover Delaware (now known as the Morris Community Correctional Center) was built. It is very likely that Frederick Jackson isn't around any longer to tell us, so if anyone recognizes anything about this old photo, please leave a comment or send me an email. Calling all Delaware Corrections Officers, how about a little help here?
If you are interested in finding out about the Jackson Family, check out Genforum.