That plastic thing on the top is called an audio cassette tape. You'd stick a pencil into one or the other of those holes if you had to manually rewind the tape. We also used stone knives and bearskins. That thing on the bottom was the protective plastic case.
Ask your grandparents if you can have one of their old Peter Frampton audio cassettes, toss it out and keep the plastic case like the one you can see peeking out from underneath. If you're lucky, there will be no annoying plastic stickers to peel off, just paper inserts you can discard.
This is how I made my own Raspberry Pi enclosure from an audio cassette tape case in which I cut holes with my Dremel.
Note the notch cut into the case closest to the camera. It is to accommodate the fact that the RCA connector is too tall to fit into the case. This lets the Raspberry Pi board slide into the niche of what's now the bottom of the case. You'll note that I've also added heat sinks to the Raspberry Pi board and have cut holes in the top of the case to accommodate them as well as the USB connector on the left.
Here we can see the hole cut into the side and top of the case to accommodate the USB connector, as well as a hole to accommodate an Ethernet cable. If you use a USB wireless Ethernet, or don't want Ethernet, you can skip this hole in the side.
I turned the case another 90 degrees counter-clockwise to take this picture:
Here we see the hole cut in this side of the case to accommodate the HDMI cable to the TV set. You'll note that it is important to make some of these holes a little bit oversized to accommodate your cable. This is less an issue than the Ethernet cable that's a little more deeply recessed as well as the USB cables that also tend to have fat plastic shields on their connectors.
This side gets two two holes: a slot for the SD card to stick out of, and a hole for the power cord.
This is another deeply recessed hole, so you'll have to make that a little bit over-sized.
Tipping the case up, we can see the top more clearly here:
Also note that because the case is transparent, you can see all the status lights on the Raspberry Pi.
Another thing. I almost forgot to mention this, because it was the first thing I did. Audio cassette tape cases can have two little tabs to engage the holes you saw in the audio cassette. These prevent the tape from sliding out.
The FIRST thing to do is to Dremel these off. You can't see where the tab on the left used to be, because I've cut a hole for the leftmost heat sink. However, you can see a cloudy haze on the right. That's the ghost of the tab on the right. I just removed enough material to make the plastic level.
A true aesthete would have polished the plastic to get rid of the ghostly fogging. I'll leave it there as an homage to Halloween. Tell your friends about the ghost picture you saw on my blog.
For completeness sake, let's take a look at the underside of the Raspberry Pi enclosure:
Some might claim that I need to remove material from the bottom of this case to accommodate the SD card socket that's protrudes slightly from the underside of the circuit board.
I think it unnecessary, but you may not.
The whole thing requires a Peter Frampton cassette tape case, a Dremel tool, and an hour or so of cutting. Oh, and I'm sorry. You really shouldn't toss out your grandparents' Peter Frampton cassette.