Mission bookshelf speakers

I have a pair of Mission bookshelf speakers that I inherited. I don't know the model number, but the serial on the back is 8VET28777. The specs on the back are:

Enclosure type: 2-way reflex
Output Power: 15 - 75 W/Ch
Nominal Impedance: 6 Ohms

I will attach a photo.

Does anyone have any idea of how much they retailed for, or how much they might be worth to sell used?

Thanks!

Check this site for info http://oldsite.mission-hifi.com/index1.htm

I picked up a pair of the same ones today for $3 plus tax at a goodwill type place. I liked the weight of them plus the very good condition. I took them home and hooked them up.
It is BY-FAR the best $3 I spent in a long time. I am talking about $3 for a cup at a keg party in the the late 80's with Frampton Comes Alive on a boom box standing in front of a fire made from pallets from the old Zayres. You get the idea.... They are clean clear and crisp. They are worth in the ball park $25-50 plus shipping. That is what I would pay knowing what I know now. Thats my $3

Don't those speakers belong with specifically that audio system? It seems like its value, if any, is as a complete set, no?