I used peters tools a few times when V5 , maybe 5 years ago… And really awesome tool. I was looking for a BOM tool. And one year ago I started on making my own scripts, having peters tools on mind for inspiration 
. But I haven’t downloaded it since the first time, because I’d like to make something different.
I’m also doing a BOM, it’s name is “Corn”, and it has capabilities to write quantity, name of block or part, xyz dimensions, material, notes. And these data are output in the command bar, separated per “,”. So it could be copied and pasted on a notepad file and save it as csv and after that opened at excel. 
I got stuck as I found an improvement on my script because a day I asked a material bigger than it really was. So I realized that when getting x,y,z I need to find the minimum material size when the part is rotated or inclined in space. 
.
I have to much work to do.
I actually just wrote a bunch of recommendations for the eventual “Mass” tool that we all hope will be available in Rhino 7 in a future update. One of the wishes was about possibility to save the mass properties in a text field, because the Command line is not convenient for copying of a long list of material properties. 
Really good ideas.
I have written another script for selection, “Bean”. Once I’ve applied materials, could be selected the ones with same material, and no material objects. Also selects no closed bodies and no named bodies, but I realized that Rhino already has those commands. So, just material interested, because of the BOM
You may also take a look at the “Solid weight” script. It’s an alternative way to calculate mass, but it’s advantage is in that you don’t permanently assign a material to the selected object. Instead, it just ask you to calculate the mass based on a material that you pick from a pop-up window, then it shows the mass in the Command line. This is especially useful for a quick examination of parts and trying to see how much they would like if they were made from a few different materials. Sadly, it only works with a single selected object, so it will not support 2 or more objects simultaneously.
in tool design is not often comparison needed. As most material used are steels and only can be replaced by other steels, or non ferrous replaced by another non ferrous, the density of these are almost similar.
In tool design more interested on:
- Mass of a part. To buy material, to make lifting holes.
- Mass of an assembly. To know the forklift or crane needed to lift it.
But I think that is a nice idea comparing . So I have to think a case where is needed . To include a feature like that
Injection moulding matrix yes, they usually rely on a specific material (mostly steels, and rarely aluminum alloys). However, in the manufacturing itself materials could vary a lot, so it’s handy to be able to quickly try cow much a manufactured piece would weight. 
It’s even more usable in CNC-machining of steel, titanium, aluminum, bronze etc parts.
Well, I’ll think about it. 
But I guess I could add something like that.
I’ve been busy on a reverse engineering project of hot stamping dies, but I can’t post images 
.
Anyway this is “Corn” 
and it’s job is doing Bill Of Material.
The list is including partname, quantity,material, dimensions and notes, now I can save a csv file.
I’d like to add more features, but at this moment I think I have to learn ETO forms and figuring out what a python class is 
, I’ve read a little bit about that, but still confused as I’m just a cnc programmer or 3D designer 
. But soon.
PD: I still working on Barley ( holemaking) but I’m planning to change the way the selections are done to make it faster to configure it and adding other functions.
In that case you might want to have a look at the bolt script I made, as that was by then the exact reason for making the script, to learn working with classes. Once you get your mind past the init and self. syntax it’s not that hard.
Thanks for the advice, I’ll study it this week until understand. Thanks 