Wavy Lines -- How To Tell If They Are A US Precancel Or Not

I have a number of stamps with these parallel wavy lines - are they precancels? Thanks.

Eg

These are roller cancels, used for cancelling stamps on packages and parcels.

Great! Always happy to exclude some of this excess of material.

I know this is kinda stupid since I can't find an example right now, but I also have some older regulars (20s-30s) with diagonal wavy lines, some with writing between them (faint, so I can't read it, but it *could* be town names). Does this sound at all familiar and can I exclude them?

There were a number of 1920's and 1930's issues that used so-called "box cancels" that is the city and state name inside a box and sometimes the vertical lines were straight and other examples show the vertical lines wavy. Here's one example from Muskegon, Michigan:



Very often they get easily confused with precancels, but they are not; they are a form of a postmark used (typically on packages) from that era.

No particular value to them, but I suppose you could certainly make an interesting sub-collection of these examples, should you be so inclined.

As for the 6-cent block you scanned earlier, again, while it is not a precancel, let me share this example from Los Angeles, California, as to what the horizontally oriented roller cancel postmark of this type typically looked like:



These sort of cancels were heavily used in the 1960's and 1970's, again, mostly on parcels or oversized items that didn't fit the normal cancelling machines.

I hope these examples are helpful.