We always hear about the shiny, new food companies. The Spot is a series about the Philadelphia area's more established establishments and the people behind them.

In 1962, when Constantine Seiss decided to open a luncheonette at 325 Chestnut Street, there wasn't much going on in the neighborhood now known as Old City. Friends thought him crazy to choose that location, but nearby Independence National Historic Park had been established six years prior, and Seiss foresaw a coming boom.

He commissioned a friend, also of Greek heritage, to build a diner-style room for him, with a pair of horseshoe-shaped counters fronting a long flat top grill. He fashioned a menu of soups, sandwiches, salads and platters, and launched the Mall Coffee Shop.

Seiss' hunch paid off, and the area around Independence Mall flourished. He was so busy during the week that he didn't even bother to stay open Saturday or Sunday. After the breakfast and lunch rushes, he'd send carts with coffee and doughnuts up to the different floors of the office building that housed the restaurant and garner even more business.

Eventually he was ready to retire, and in 1988 he sold the business to Jerry Kahrilas, a fellow Greek who'd been director of catering services for the Philadelphia Sheraton. Kahrilas renamed the spot after his wife, dubbing it Mrs. K's Koffee Shop.

In 1992, Kahrilas' partner Philip Nicholades assumed full ownership, and he oversaw things through 2007, when he sold it to yet another Greek couple, George and Vasiliki Konstantopoulos. Two years later, Mrs. K's was sold again, landing in the hands of Christos Koumboulis.

Koumboulis fell in love with the historic nature of the shop, which still had all its original furniture and kitchenware. He interviewed Constantine Seiss and set about restoring Mrs. K's menu to align with Seiss' original vision - not a overload of cheap food like a regular diner, but a more pared-down menu of quality choices. Though the shop was busy and successful, landlord disagreements led Koumboulis to seek exit from the business, and in early 2012 he sold to Nouman Shubbar.

At the time, Shubbar knew nothing about restaurants. A longtime Philadelphia police officer, he had a full-time job serving on Philly's FBI Joint Terrorism Task Force. However, he and his brother, a pharmacist, had been looking for a small business to invest in on the side. When they heard Mrs. K's was up for sale, they decided to jump into the hospitality game.

Nearly four years later, Shubbar, 52, knows a lot more about the food biz. He's learned about refrigeration maintenance and menu development, grill cleaning and ingredient sourcing. He added late-night hours on Fridays and Saturdays to take advantage of the neighborhood's bar scene, and spends money to advertise on Yelp.

Armed with a 16-oz. cup of very decent Lacas coffee, he took 30 minutes out of his busy policing schedule to sit on one of Mrs. K's stools and discuss his pet side project.

Why buy a restaurant?

My younger brother is a pharmacist in Western Pa., and for years he was always making suggestions of places we should invest in - let's buy a gas station, let's buy a grocery store. Through a friend, I heard this place was for sale. Mind you, I had no experience in any kind of restaurant - my only experience was washing dishes as a student, when I was in college. But I figured, why not give it a try? So we bought the place. He lives far away, so I handle the day-to-day.

Where do you find the time, since you have a full-time police job?

Well, thankfully I have my mother-in-law, Carol Ferrier, who's here during the week. My wife Nancy is here on Saturdays, and a woman who's worked here for a very long time does Sundays. My role is mostly things like hiring the staff, dealing with vendors, and if there's a problem that needs to be fixed, I make the phone calls. Also I'm here Friday and Saturday nights - I added those hours, 6 to 3 in the morning, because of the big bar crowd.

How did you learn about the restaurant business?

I mostly winged it and learned from my mistakes. I also go to places like IHOP - big corporate places that have the money to do research - and watch how they plate their food, what they have on their menus. Because I really knew nothing before I started.

Funny story about my first day as owner. I was the only one here, it was early. This lady walks in and says, "I'd like a coffee," and I'm completely terrified! Because I realized I didn't know how to operate the coffee machine. I mean, it's not rocket science, but if you haven't done it, it's like, what do you put where? When do you press which buttons? I froze. Luckily, the previous owner's mother came in right then - she was helping us out for a few weeks to smooth the transition - and she took over. I was like, "Oh, thank God."

Did you make changes when you took over?

At first we pretty much kept everything the same, but little by little, we did some tweaks. Mostly behind the scenes. I put in a new air conditioning system, new kitchen equipment and sealed off the kitchen floor. I tweaked the menu a little bit, found a new bread supplier (Aversa). I got a sidewalk license and added outdoor seating. I added the weekend nighttime hours, and also tested staying open on holidays.

Are you ever closed?

Now, we close only on Christmas Day; we're open 364 days a year. When I took over, they used to also close on Easter, Thanksgiving and New Year's. I did it incrementally - tested each one. I actually worked here this Thanksgiving, because I was off from police work, and I got totally overwhelmed, because it was our first time being open and I only had a skeleton crew. Now I know it will be busy. Same with New Year's Day, we tested it last year and it was very busy.

Is your business more from regulars or tourists?

There are definitely a lot of regulars, especially the people who work in this office building. But tourists are also a big component. I always let all the hotels know that we're open, and you can get breakfast all day - a lot of hotel guests come in for that.

Do you do advertising?

I do pay for Yelp. And sometimes I put an ad in the local Old City paper. It's expensive! Otherwise I would do it more. But the location is a big help. There is a lot of foot traffic.

Best-sellers on your menu?

For the tourists, it's the Philadelphia specialties, like the scrapple and cheesesteaks. Our cheesesteaks are very good; people love them. And breakfast - we make our own homefries here from scratch every day.

So has it turned out to be a good investment?

It has, but it's hard work. I didn't know how hard it would be.

Advice for someone who wants to get into the restaurant business?

Think about it twice - or three times - before doing it, because it's a lot of work. You have to always be there, or somebody you trust has to always be there. I used to enjoy going on vacation, but now I don't go anymore, or if I do, it's for two or three days. And maybe work in another restaurant first, so you get a good idea how to do things.

Any plans for the future?

There's only so much we can do here - we're stuck with this size space. But whoever designed it was very efficient. We have 50 seats, and the space is used very well. Also, this building is being sold, and my lease is up in 2017, so I don't know what the new landlords will do. The place has been here so long - I hope they let us stay.

Mrs. K's Koffee Shop
325 Chestnut St., 215-627-7991

Hours: 6 a.m. to 3:30 p.m. Monday to Friday, 7 a.m. to 2:30 p.m. Saturday and Sunday; 6 p.m. to 3 a.m. Friday and Saturday