I am guessing it is a single ply of random woven mat fibers. THey have ratings up to 5400 N/mm for special belts. These belts can withstand very high impact loads from big rocks.

Google says:

include: nonwoven fabrics, sleeves or wraps, blankets or batts, woven fabrics, knitted fabrics, carded or needlepunched non-wovens, and braided fabrics. Nonwoven fabrics are textile- or fiber-based materials shaped into mats of randomly-oriented fibers

Some random fiber mats are made of Kevlar with very high tensile ratings. ■

The random woven belts are quite thick, very stiff, and do not trough well.

By memory, they are flat belts used as feeders and with high impact installations.

Splicing is a dilly. ■

What exactly is a "Dilly" Larry? ■

Dilly:

Synonyms: beaut, beauty, bee's knees, cat's meow, corker, crackerjack (also crackajack), daisy, dandy, jim–dandy, doozy (or doozie also doozer), dream, honey, hot stuff, humdinger, hummer, knockout, lollapalooza, lulu [slang], nifty, peach, pip, pippin, ripper, ripsnorter, snorter

My use was more akin to " Lulu" as in "it's a doozy or a humdinger". I liked Lulu, as I told my kids when they asked: "where are we going dad - I'd say to Lulu's house?"

Goosh, I thought you were of my vintage? ■

Ah-ha!

I thought it was a diminutive of "Dilly-Dally" which, according to Chambers dictionary, means...."To waste time"... which one would hardly wish to do,..... when performing a belt splice...

Cheers ■