Can סכינים really take either the feminine or masculine number?
yes. not so common. i guess most people just endorse one way and stick to it. i use feminine
http://hebrew-academy.org.il/2010/10/05/%D7%9E%D7%99%D7%A0%D7%9D-%D7%94%D7%93%D7%A7%D7%93%D7%95%D7%A7%D7%99-%D7%A9%D7%9C-%D7%A9%D7%9E%D7%95%D7%AA-%D7%90%D7%97%D7%93%D7%99%D7%9D/
this is what the acadmey of the hebrew language have to say about nouns that are both masculine and feminin
תודה רבה אחי
So do I.
Interesting! Good to know
Even though this is implicitly showing that the word סכין can be either masculine or feminine, it's still quite the confusing sentence!