The age on Jacob's tombstone is not consistent with his age in the censuses.

The age on Catharine's tombstone is not consistent with her age in the censuses.

— born in Mangenhart, Baden [Germany]:
  7.  Christina SCHREIBER, b. 8 Jan 1837; d. 3 Jan 1913, Yates Center, Woodson Co., KS
  8.  (Daughter) SCHREIBER, b. bef. 1846; d. bef. 1846
  9.  (Daughter ) SCHREIBER, b. bef. 1846; d. bef. 1846

— born in Ridott Twp., Stephenson Co., IL:
10.  Carl Eduard / Charles Edward SCHREIBER, b. 1847; d. aft. 1919
11.  Simon SCHREIBER, b. 8 Apr 1851; d. 14 Oct 1911, Freeport, Stephenson Co., IL 

12.  Elizabeth "Lizzy / Lizzie" SCHREIBER, b. 26 Aug 1856 
Anna Catharina was 47 (almost 48) years old in 1856.  Might Lizzy be adopted?  Has a generation been skipped?  Otherwise, Lizzie married the brother of her sister Maria's son-in-law.

Then, of course, there's this child, living with them in the 1870 census:
.  Hillers(?) SCHREIBER, b. 1858/9
It seems beyond the realm of biological possibility that he could be our subjects' son.

1.  Marriage Record:

2.  1850 Census Index/Images (online at Ancestry.com; Image #7 of 16 — indexed "Schriver"):  Town of Ridott, Stephenson Co., Il, p. 382A/755, enumerated 12 Nov 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

1880	1879	Salome Faustis?	55	F			2000	Germany
		Edwin?     "	14	M				"
		Catherine Gatwig	62	F				"
	1880	Jacob Schriver	52	M		Farmer		"
		Catherine  "	42	F				"
		Jacob      "	20	F		Do		"
		Frederic   "	18	M		Do		"
		Catherine  "	17	F				"
		Mary       "	15	F				"
		Elizabeth  "	13	F				"
		Christina  "	12	F				"
		Edward     "	3	M				Ill

Catherine GATWIG/GARWIG appears to be Catherine SCHRIVER's mother.

3.  1860 Census Images (online at Ancestry.com; Image #28 of 645 — indexed "Swiber"):  Ridott P.O., Town of Ridott, Stephenson Co., IL, p. 28, PN 28, 196/185, enumerated 8 Jun 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Jacob Shriber	61	M		Farmer	2400	500	Baden
Catharine  "	51	F					"
Jacob      "	30	M		Farmer		400	"
Mary       "	26	F					"
Frederick  "	2	M					Illinois
Henry      "	1	M					"
S.A.       "	2/12	F					"
Edward     "	12	M					"
Simon      "	9	M					"
Lizzy      "	4	F					"
Georg Hapster	30	M		Laborer			Baden

Mary is the junior Jacob's wife, not his sister.  Is Lizzy really Catharine's daughter?  Having a child at age 48 is extraordinary.  Was Lizzy adopted?  Living next door to them is George SHRIVER (æ 12, b. Baden), who appears not to be related to our subjects.

4.  1870 Census Index/Images (online at Genealogy.com; Image #31 of 50 — indexed "Schrider"):  Ridott P.O., Ridott, Stephenson Co., IL, Roll 275 (Book 1), p. 268A, PN 31, 240/233, actual enumeration date not given, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Schriber Jake	71	M	W	Farmer			Baden
________ Catharine	61	F	W	Keeps house			"
________ Simon	19	M	W	At Homer			Ills
________ Lizzie	13	F	W				"
________ Hillers?	11	M	W				"
Alden John	19	M	W	Farm Laborer			Hanover

5.  LDS.  Family Search: Census Records: 1880 United States (online at FamilySearch.org):

Census Place: Ridott, Stephenson, Illinois
Source: FHL Film #1254253; NARA Film #T9-0253; Pg 234B
	Relation	Sex	Marr	Race	Age	Birthplace	Occupation	Fa	Mo
Simon SCHREIBER	Self	M	M	W	29	IL	Farmer	BADEN	BADEN
Louisa SCHREIBER	Wife	F	M	W	28	IL	Keeping House	PRUSSIA	PRUSSIA
Jacob SCHREIBER	Father	M	W	W	81	BADEN		BADEN	BADEN
Jacob KRYDER	Other	M	S	W	21	PA	Laborer	PA	PA

6a.  Tombstone Readings:  North Grove Christian Cemetery, Ogle Co., IL (courtesy of Roger Cramer):

Jacob Schreiber, died Dec. 5, 1882, 88y/7m/20d

Catharine Schreiber, wife of Jacob, died October 12, 1879, 79y/4m/12d

Also buried next to them is Catharine Garwig, wife of Charles died August 13, 1869, 81y/11m

Note that Jacob's ages in the censuses were 52 in 1850, 61 in 1860, 71 in 1870, and 81 in 1880; yet, his tombstone says he was 88 in 1882.  Note that Catharine's ages in the censuses were 42 in 1850, 51 in 1860, and 61 in 1870; yet, her tombstone says she was 79 in 1879.  Please see the next source. 

6b.  The Accuracy of Death Certificates and Tombstones:  or why we should rely more on Jacob's and Catharine's ages in the censuses than on their ages on their tombstones. 

6c.  Birthdate calculated using Ben Buckner's JavaScript Birthday Calculator.

Name	Deathdate	Age at Death	Result
Jacob SCHREIBER	05 Dec 1882	20d 07m 88y	15 Apr 1794
Catharine SCHREIBER	12 Oct 1879	12d 04m 79y	30 May 1800
Catharine GARWIG	13 Aug 1869	00d 11m 81y	13 Sep 1787
(Calculated birthdates should always be prefaced with "ca." — you can't be certain the person who calculated their age did it correctly.)

Catharine GARWIG's age at death is consistent with her age in the 1850 census.

7.  Email from Dennis Stephens; also, his Descendants of Jacob SCHREIBER.

8.  Email from Roger Cramer; see Roger & Sue Cramer's Genealogy Site.