A picture of the top of your receiver would help, but after looking at a Google image search of "Mossberg 195", is the dovetail the entire length of the receiver or is it only under the rear sight? It differs.
If it's the entire length, there are one piece scope mounts like :
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....that you can place ahead of the ejection port to mount a scope. If the dovetail is only as long as the rear sight...you probably don't have enough rail to support a mount. You would only have enough rail for one ring, and I wouldn't try that on a slug gun.