Debris found in oil filter

[apbright]

Just for curiosity, during a recent oil change, I ripped open the oil filter, to see what one can find inside. On the inlet side of the paper in the filter, I found some metal particles, per the photo. The particles are mostly max 1/16th-inch, a few slightly longer. Is this normal, or the sign of something having gone wrong.

For what it's worth, the engine was rebuilt about 8000 miles / 1 year ago, converted to insert bearings. About 80% of those are highway miles at 55-60mph with a Mitchell 26% OD, stock rear end. The filter is the standard PH8A, on a 'full flow' filter kit.