Der all, just to geh this wheel correct described (I hope I have nothing forgotten...)

Types of this wheel available:
Petri Type 838 (registration KBA 7003)
a) with solid hub, screwed on wheel (not same as E9 CSL, bore belt is wider) and movable inner BMW logo as horn button (logo same part number as the well known silver spoke Petri), solely available for e10, e12.
So called Turbo wheel (correct BMW description Sicherheitssportlenkrad- safety sports steering wheel), indicated on back either with 38 or 838, depends on year of production. 38 cm diameter.
b) same as a) but in 36 cm only for e10
c) same as a) but with flat "all pressing" hard plastics horn button, for e12, e23 and e21 early models
d) same as c), but with crash collapsing riveted woven hub.
e) same as c) but with more solid horn button made of rubber foam.
f) same as e) but in 40 cm diameter (rarest Type 8xx Petri wheel with BMW hub - more often sold for Ford Granada, Consul, Capri)
The solid hub was just changed in 1975 to crash collapsing one due to German StVZO (street permission legislation). Same time the KBA numbers occurred. Petri than changed numbering of the wheels from 3x to 836, 838, 840.
On the same wheels sold on the free market, from 1975 the KBA was stamped and same time those wheels were established in parallel with the oval holes in the spokes and a center bolster. This wheel was also officially sold then by BMW for e10 some while. Opel Kadett and Ascona had them from factory.
As a car part in Germany is installed from factory till 1977, it doesn't need a KBA on it.
For the well known 35 ,38 and 40 cm Perri wheel (silver spokes), BMW requests a special allowance for 1977s 1502 models to proceed without KBA.
Hope my essay

is understandable
I have pictures of every referenced wheel above, more or less also for every wheel the registration papers on hand.
If someone needs something for reference just let me know