Need Assistance In Identifying Theses Liberty Postal Cards

I have many Postal cards, many of which are of the Liberty type. I did not realize their were several types. Is it worth figuring a watermark? Also, how would you detect watermarks on these older cards? I dont want to ruin any of them if it'll hurt their value. Thank you, Treina

There are three of these cards;
UX4 is watermarked with a small "USPOD" in monogram Hope you find one or more! To see warermarks you can try looking at them with strong light behind it or any Watermarking fluid, like Clarity, or lighter fluid, Ronsonal or zippo. will work, Black background.
The second card UX5 is unwatermarked. They both are inscribed WRITE THE ADDRESS.
The 3rd card, UX7 is inscribed NOTHING BUT THE ADDRESS. The last two are fairly common.

Exactly what I needed to know LRP. Much gratitude for your time.

Treina