Petals are whitish toward the center, with a lighter silvery reverse.

The found rose "Jay's Hudon Crimson" in the Historic Rose Garden of the Sacramento Old City Cemetery has growth habit, cane color and armature identical to "Old Town Novato."

I have studied the found Hybrid Perpetual "Old Town Novato" and can add these details with the hope someone can suggest an identification.

The color of the petals, front and back, of "Old Town Novato" is intermediate between 'Baronne Prévost' and 'Ardoisée de Lyon.' They bloom in the spring at the same time. "Old Town Novato" reblooms freely.

Other major differences are:

"Old Town Novato" has around 80 to 100 petals and petaloids. The petal form is cuneate (wedge-shaped). The point of attachment is pale lilac to white.
'Ardoisée de Lyon' has around 130 petals and petaloids. The petal form is emarginate (wider than long with a pronounced notch in the middle). The point of attachment is pale lilc to white.

The outer petals of the blooms of "Old Town Novato" open out and reflex.
The outer petals of 'Baronne Prévost' and 'Ardoisée de Lyon' tend to cup upwards and maintain that form.

The blooms of "Old Town Novato" are deeper, looser and less disk-like. Disbudded, the blooms easily and consistently reach 5 inches/12.5 cm on an unfertilized rose.
The blooms of 'Baronne Prévost' and 'Ardoisée de Lyon' are more tighter, flat and disk-like.

The sepals of "Old Town Novato" of often large, long and foliate.
The sepals of 'Baronne Prévost' and 'Ardoisée de Lyon' are lanceolate, with only two or three very small appendages.

"Old Town Novato" bears bloom in clusters of as few as 5 and as many as 19 on new basal canes.
'Baronne Prévost' and 'Ardoisée de Lyon' bear blooms singly.

There was a time I thought the most likely identification of "Old Town Novato" was Ardoisee de Lyon. However, after growing the two together for a while, I've concluded they are not the same.