Loved one knows husband at times & other times asks him where husband is. She can call him on her cell. Is she being manipulative? Has Alz.

Not likely a person that far along in dementia can be that manipulative. And to what end?

Someone once told me that their SO wasn't 'suffering' at all from dementia, that they seemed perfectly happy most of the time, the 'stuff' that dominates all of our lives was simply not registering.

This is the desease. And I agree, show her a picture of you younger. Those suffering from a Dementia tend to go back in time. So you wife maybe back in her 30s so this old man in front of her is no way her husband. The mind is dying or broken, as some call it. She is in her own little world and you need to learn to be a part of it. She can no longer function in this world. Just agree don't try to tell her differently.

Some times my Mom knows me as her daughter. Some times my Mom knows me as the nice lady who takes care of her. The first time she didn't know who I am, was like a punch in the gut. But, imagine how terrifying it is for the person with dementia.
Unless there is a history of manipulation, families tend to assume some type of manipulation because they fear facing the reality that their loved one is experiencing BRAIN DEATH. Just like some diseases destroy other organs, this one destroys the brain.
Wires get crossed, sections of memory stop be accessible, sometime for a short period other times for much longer. It's all hit and miss. But, at the same time, the demented are trying to patch it all into some type of coherent story for themselves.

I woner if her husband could get a copy of a past picture of himself along with a current picture and place side-by-side with his name in a badge? This way he could wear it whenever his wife starts asking for him or who he is.

My guess is that because she is well into her Alzheimer's disease, that she honestly is just confused as to who is who. And of course it's very common for someone with Alzheimer's/dementia to sound and act very normal at times as well. It's all part of the disease. Her brain is broken and will never get better. I would just go along with whatever she says and does at this point. Best wishes.

One can only guess on this one, I suspect. I would ignore it completely, or answer gently and simply, and move on.