A toy stethoscope, sized for a small child.
If you're lucky it might be (slightly) functional.
I can sometimes hear a heartbeat if both ends are held firmly.
To finish this you'll need some 1/4 inch / 6.5mm flexible plastic tubing.
Print two each of "pipe" and "earpiece", and one each of the other two parts.
Ridiculous disclaimer: this is a toy, don't try to use it as an actual medical device.
Glue the "earpiece" parts to the curved ends of the "pipe" parts.
Glue the straight ends of the "pipe" parts into the round holes (holes without clamps) in the "neck spring".
You might need to file the ends of the "pipe" parts to get them to fit - they are quite tight.
When the glue is dry, cut two equal lengths of plastic pipe and use them to connect the "trumpet" to the two sides of the "neck spring".
You'll need to squash the ends of the pipes to get them through the clamps and into the holes.
On my one, the plastic tube is clamped very tightly and won't easily come out when pulled.