It's what has typically been referred to as a "Malerne Stencil"...made in France.
I say it in this manner because while, indeed, Malerne had a factory which assembled saxes, and the ones engraved Malerne are identical to ones like this, it may well be that the parts were sourced from Santoni, Italy ...and possibly even some fabrication done in Italy. Sometimes these read France or Italy on 'em...sometimes not.
So it's one of those...apparently a ubiquitous model throughout Europe in the 50's-70's. Tulip motif in the bell keyguard, vertical serial number, 'arrow' style neckbrace and the table shape are some of the telltale features. Also the bellbrace wire has a square cross-section, not round.
Good vintage horns, quality-wise. Well-made, not chincy...they sound absolutely wonderful. Big and wide and dark, The keywork is okaaaay...no worse than a lot of other vintage horns of the same era, like a Conn 16M or the like....but not exactly quick in the action, particularly the table.
$500 is the price of what one which has been serviced and is guaranteed to play should go for. Back in the day I'd sell a lot of these, they were just good, robust, ballsy, cheaply priced Tenors with a lotta cojones. But the market cares little about them nowadays.
So, this one, needing a tech visit, is worth perhaps $200-ish as it is described.