I have experienced this a couple of times recently when I've been out and about.
I'm 51, and since the weather is cooler here right now I usually wear tall leather boots, skinny jeans, and a nice thick sweater. I have enough boobs for them to show under the sweater, but I'm not super stacked or anything. I'm also just a bit taller than average for a female at 5'8", I'm not overweight, but I do have a larger upper torso. I'm told I have a nice butt. My hair is a strawberry blonde wig that is shoulder length (I hate wearing a wig but it is a necessity right now). I'm aiming for a hip, nicely dressed, middle aged suburban mom look. I've observed in my time out in the world en femme that people generally don't give me a second glance.
So anyway, one time I was at a restaurant and a guy eating lunch with his wife turned sideways in his booth to face me (I was at the table across the aisle from his table) and he stared at me for a full 30 minutes. I just kept eating and ignored him. The other time I was leaving a store and a guy was walking into the store and he gave me a long, long stare. I found both experiences creepy. I remember checking out women in guy mode but I did it far more subtly than these two dudes did.
What they saw or thought? I have no idea.
Women on the other hand smile at me now which is nice. In the same restaurant with the creepy staring guy a female employee went out of her way to smile at me, and to say several nice things to me. I was in a mall recently and a group of people were waiting for an elevator. A woman was there with her teenage daughter and the daughter was having some kind of teenage angst. The mom corrected the daughter and then looked at me with a knowing smile and I smiled right back because I have been there before with my own daughters.
Being on the other side of the gender fence has really opened my eyes about guys & guy behavior. Thank heavens I don't have to endure the effects of testosterone any longer.