WC845, aka SMP 845.
The data sheets I have for it, say that it is 1/2 grain faster than H335. Use H335 start loads as MAXIMUM & reduce by 15% if no start load is shown. It also says Best for .223.
It is reported to be a slower lot of 844 / faster lot of 846, which, once upon a time, were just 1 powder, which was then renamed into 2 lots, the faster 844 for 5.56 (.223), while the slower lot 846 was designated for 7.62 NATO (.308 WCF)
On the included burn rate chart, it is right next to AA2460 & before H335.
A quick cross-check with Quickload reflected a Speer 145 gr. BTSP moly-coated bullet, in a 29" barrel, yielded 2,487 fps using 37.0 grs. of AA2460, and 2,350 fps in a 23" bbl. Both reflected a breech pressure of 34,026psi.
The only fly in the ointment is that, at least for the Czech AA2460, it occupies only 67.9% of net case volume, assuming a gross water capacity of 59.5 grs. of H2O & a C.O.A.L. of 3.071".