All depends on condition and originality. To be top dollar it would have to have original blue, correct metal buttplate and sling swivels, the barrel tuner under the forearm, and the original Brno sights. There should be a dovetail at the muzzle where the front sight block would mount if that's what you mean by a flat spot. Not sure if you mean the scope is mounted directly to the 16mm receiver rail or to an adaptor. Many of these were factory or importer refinished and will have a dull blue or parkerized looking finish. There may be an importer mark such as Svazarm if it has been redone. Look for the date stamp on the left hand side of both the receiver and barrel. It will be somewhere between 49 to 56. The barrel will be 26 1/4" to the receiver if uncut
You can get the correct Brno aperture sights from a fellow in California. I would think the whole set would run $200 by the time you got everything.
I have bought 2 of these in the past year and would say $650 max without the sights if in very good condition. You'll have to figure the scope value separately.