Maria Peterstr. Oikimus Parkko (Petrova) - Mysterious "Parkko" extra last name

Here is the link for the profile: Maria Peterstr. Oikimus Parkko

At first I thought perhaps she was married before to a man with a family-name Parkko, but she is too young to marry someone else before she married Walter Oikimus.

Second option could be adoption. Do we know when her parents died? Perhaps her aunt Pelageya Vasilyeva and her husband Simo Parkko officially adopted her, if her parents had died while she was young?

Wanted to write her husband Andrei Oikimus and not Walter Oikimus in the last post. This happens when you write a post before having your morning coffee.

Good guess! That means any lists of family members between 1904-1922 of Pelageya and Simyon should have Maria as well. Also, a marriage record might help in case there is some info about the maiden's last names.