Acronym 2n,2m-dip
Name 2n-gonal - 2m-gonal duoprism
General of army (is itself convex)
Colonel of regiment (is itself locally convex)
Especially 4,2m-dip (n=2)
Confer
general duoprisms:
n,m-dip   n,n-dip   2n,m-dip
External

Incidence matrix according to Dynkin symbol

```x2no x2mo (n>1,m>1)

.  . .  . | 4nm |   2   2 |  1   4  1 |  2  2
----------+-----+---------+-----------+------
x  . .  . |   2 | 4nm   * |  1   2  0 |  2  1
.  . x  . |   2 |   * 4nm |  0   2  1 |  1  2
----------+-----+---------+-----------+------
x2no .  . |  2n |  2n   0 | 2m   *  * |  2  0
x  . x  . |   4 |   2   2 |  * 4nm  * |  1  1
.  . x2mo |  2m |   0  2m |  *   * 2n |  0  2
----------+-----+---------+-----------+------
x2no x  . ♦  4n |  4n  2n |  2  2n  0 | 2m  *
x  . x2mo ♦  4m |  2m  4m |  0  2m  2 |  * 2n

snubbed forms: s-2n-o-2-s-2m-o
```

```xnx x2mo (n>2,m>1)

. . .  . | 4nm |   1   1   2 |  1   2   2  1 |  2 1 1
---------+-----+-------------+---------------+-------
x . .  . |   2 | 2nm   *   * |  1   2   0  0 |  2 1 0
. x .  . |   2 |   * 2nm   * |  1   0   2  0 |  2 0 1
. . x  . |   2 |   *   * 4nm |  0   1   1  1 |  1 1 1
---------+-----+-------------+---------------+-------
xnx .  . |  2n |   n   n   0 | 2m   *   *  * |  2 0 0
x . x  . |   4 |   2   0   2 |  * 2nm   *  * |  1 1 0
. x x  . |   4 |   0   2   2 |  *   * 2nm  * |  1 0 1
. . x2mo |   q |   0   0  2m |  *   *   * 2n |  0 1 1
---------+-----+-------------+---------------+-------
xnx x  . ♦  4n |  2n  2n  2n |  2   n   n  0 | 2m * *
x . x2mo ♦  4m |  2m   0  4m |  0  2m   0  2 |  * n *
. x x2mo ♦  4m |   0  2m  4m |  0   0  2m  2 |  * * n
```

```xnx xmx (n>2,m>2)

. . . . | 4nm |   1   1   1   1 |  1  1  1  1  1  1 | 1 1 1 1
--------+-----+-----------------+-------------------+--------
x . . . |   2 | 2nm   *   *   * |  1  1  1  0  0  0 | 1 1 1 0
. x . . |   2 |   * 2nm   *   * |  1  0  0  1  1  0 | 1 1 0 1
. . x . |   2 |   *   * 2nm   * |  0  1  0  1  0  1 | 1 0 1 1
. . . x |   2 |   *   *   * 2nm |  0  0  1  0  1  1 | 0 1 1 1
--------+-----+-----------------+-------------------+--------
xnx . . |  2n |   n   n   0   0 | 2m  *  *  *  *  * | 1 1 0 0
x . x . |   4 |   2   0   2   0 |  * nm  *  *  *  * | 1 0 1 0
x . . x |   4 |   2   0   0   2 |  *  * nm  *  *  * | 0 1 1 0
. x x . |   4 |   0   2   2   0 |  *  *  * nm  *  * | 1 0 0 1
. x . x |   4 |   0   2   0   2 |  *  *  *  * nm  * | 0 1 0 1
. . xmx |  2m |   0   0   m   m |  *  *  *  *  * 2n | 0 0 1 1
--------+-----+-----------------+-------------------+--------
xnx x . ♦  4n |  2n  2n  2n   0 |  2  n  0  n  0  0 | m * * *
xnx . x ♦  4n |  2n  2n   0  2n |  2  0  n  0  n  0 | * m * *
x . xmx ♦  4m |  2m   0  2m  2m |  0  m  m  0  0  2 | * * n *
. x xmx ♦  4m |   0  2m  2m  2m |  0  0  0  m  m  2 | * * * n

snubbed forms: sns2sms, sns2smx (for even m)
```