I have a Phoenix which is a different brand but I guess the companies had a degree of influens on each other. These Adlers are definitely gems. Some insist they are all metal, but the one I came a cross had a few plastic gears. I guess some were all metal, others not and they experimented a bit in those days. All metal gears would be a pluss.
The 189 was top of the line in the 1950s, it takes double layer cams giving fancy stitches few other models could at the time. In clean, working order you could get a bit for it. Used sewing machines like this go for anything from $70 to $200 around here, but it gets harder to find a buyer much above $100. Then they have to be in fully working condition, accessories and cams need to be there, clean, oiled and stitch samples provided. Adlers aren't very common and yours looks like it's in very nice condition.