The gun predates the more popular military and sporting Mannlichers.
Namely, the 6.5x54 Mannlicher-Schonauer, and the even-later 6.5x52 Mannlicher-Carcano.
The 6.5x53R Dutch and Romanian Mannlichers are somewhat forgotten by the collector's crowd, although they do turn up in daylight every now and then. I have two of them, the cavalry carbine above, and an engineer's carbine. Ammo is not readily available, although custom formed brass and completed rounds can be bought, for a premium. The proper 5-round en-bloc clips are necessary for repeater functioning, otherwise the gun is just a single-shot bolt action. I ended up with a lot of ammo and clips, but sometimes you can find sources of the clips in Shotgun News or The Gun List.
The gun is fun to shoot, as stubby as it is. The bolt is as smooth as glass in operation, and when chambering the 5th round from the clip, the empty clip simply drops through the slot in the magazine floor. The gun is ready for another full clip when you open the bolt after firing the 5th round.
I don't know what the value is on these guns, I haven't even seen one listed in Fleyderman's Blue Book of Gun Values. Several variants were produced, to include a full-length infantry rifle. Around WWII, some in the Dutch East Indies were rechambered for the bigger .303 British round. (Ouch!) Randy Rick's website talks about the Dutch Mannlichers, among other Mannlicher variants.
Wish I could be more help, maybe somebody else will chime in with the particulars concerning value and scarcity.