I suppose it depends on the timeline of the album. If it grew 'organically' then the earliest photos would be at the beginning and as Carol said, and new photos would be added over the years, as they were acquired.
If you look at the photos at the beginning of the album and then at those at the end of the album, presumably there is a substantial time difference as you mention 1800s to mid 1900s? As the first photo is a wedding photo, perhaps the book was given as a wedding gift to Leila and Melchior. Obviously if you know when they married you have an approximate date for the start of the collection of photos.
You mention 36 photos - is that all that there are in the album?
I would say that the only way you may be able to identify the unknown people is to ask other family members if they recognise them.