[groff] How does one recreate the \(bs symbol?

[Stephanie Björk]

Sorry if the context is out of the ordinary, but I would like to have some
specifications of the \(bs symbol, which does not seem to exist on Groff.
I am quite certain that it can be recreated using Troff's drawing
primitives, but I can't seem to get it quite right.  Perhaps someone has
the exact or an almost exact specification saved somewhere?

Here is the best imitation I could come up with, which is still an eyesore:
\h'-0.1n'\z\(ci\h'+0.1n'\v'-0.25n'\z\D'l 1n 0'\v'-0.25n'\z\D'l 1n
0'\v'-0.25n'\z\D'l 1n 0'\v'-0.25n'\z\D'l 1n 0'

If someone has done something similar and has a better specification,
please tell me about it.  And I also hope the original author does not mind
me using it in an open-source sed script of my own.  Thanks.  :)