Yes, it's brass, as is the objective cell, dew shield and some smaller parts - possibly the focuser, too. I'm not sure about the OTA, but I think it's some type of aluminum.
Charlie
So a funny, (not so), thing happened on the, (my), way to the, (this), forum. Or sometimes brass is a PITA!
Last week I set up three Nippon Kogaku examples in the garden for a photo shoot in the daylight. Afterword I carried them out the garden gate and in the waning light adjusted their finder scopes, sighting on a cell tower 3 miles distant. I had a passing thought that how cool it was that I had all the caps for finders and objectives, (you don't always get all the bits and bobs when buying used). After night fell I caught a few minutes observing with all 3 scopes just ahead of a storm front moving in. I packed everybody into the house and in the morning I found one finder cap on the kitchen counter. Just one.
I spent the morning going through my pants pockets, shirt pocket, sweatshirt pocket (pouch?), all of the flat spots in the house where I might have set the missing caps. The telescope cases, pockets in clothes I know I wasn't even wearing the night before. Checking not once but multiple times!
When the daylight got stronger I started scanning the lawn, (which was long enough that my footsteps left a trail). After a while I saw cap 2! I had already tested the cap that I had found in the house with a very large magnet and of course nothing ferrous there. Brass is a PITA). I spent the next few hours raking the lawn with my fingers, massaging the grass and clover over about 600 square feet. I took off my shoes and walked all over hoping to feel cap 3 barefoot...nothing. I traced my path to the wood shed, out to the mailbox, anywhere it might have wiggled out of a pocket. This added quite a few thousand square feet to the search zone. More nothing.
So a few options ran through my mind... It was only 600 square feet.
Spray the most likely area with Roundup herbicide and wait 3 weeks for it to turn orange and wilt down, Voila! Nah.
Better idea use my propane weed flamer to reduce the lawn to ash. Probably wouldn't melt aluminum or brass?
Better yet, rent a metal detector! Two roundtrips to town to rent and return = 80 miles. Rental $22 for 4 hours. Sure why not. Greta forgive me, I'm suffering from Nikon-its!
Long story/short, (I know too late for that now), I did find it finally. I got a strong signal but when I massaged the grass I couldn't feel anything. I was about to return the detector when I returned to that spot again. To eliminate the assumption that I was just picking up the scent of a lost garden fence staple below ground I dug a shallow plug of sod and soil and ran the detector over the hole and the plug. The plug beeped the hole didn't. I massaged the veg on the plug and still nothing, turned it upside down, gave it a hard shake and success!
We look for things. We are nothing if not persistent. Gotta love DS9!
Photo of no longer missing cap and habitat it was found in.
Photo of Goto finder cap with mitten, (dummy?), string.